@Nullable
 private PyType getReturnType(@NotNull TypeEvalContext context) {
   for (PyTypeProvider typeProvider : Extensions.getExtensions(PyTypeProvider.EP_NAME)) {
     final Ref<PyType> returnTypeRef = typeProvider.getReturnType(this, context);
     if (returnTypeRef != null) {
       final PyType returnType = returnTypeRef.get();
       if (returnType != null) {
         returnType.assertValid(typeProvider.toString());
       }
       return returnType;
     }
   }
   final PyType docStringType = getReturnTypeFromDocString();
   if (docStringType != null) {
     docStringType.assertValid("from docstring");
     return docStringType;
   }
   if (context.allowReturnTypes(this)) {
     final Ref<? extends PyType> yieldTypeRef = getYieldStatementType(context);
     if (yieldTypeRef != null) {
       return yieldTypeRef.get();
     }
     return getReturnStatementType(context);
   }
   return null;
 }
 @Nullable
 @Override
 public PyType getReturnType(@NotNull TypeEvalContext context, @NotNull TypeEvalContext.Key key) {
   for (PyTypeProvider typeProvider : Extensions.getExtensions(PyTypeProvider.EP_NAME)) {
     final PyType returnType = typeProvider.getReturnType(this, context);
     if (returnType != null) {
       returnType.assertValid(typeProvider.toString());
       return returnType;
     }
   }
   if (context.maySwitchToAST(this)
       && LanguageLevel.forElement(this).isAtLeast(LanguageLevel.PYTHON30)) {
     PyAnnotation anno = getAnnotation();
     if (anno != null) {
       PyClass pyClass = anno.resolveToClass();
       if (pyClass != null) {
         return new PyClassTypeImpl(pyClass, false);
       }
     }
   }
   final PyType docStringType = getReturnTypeFromDocString();
   if (docStringType != null) {
     docStringType.assertValid("from docstring");
     return docStringType;
   }
   if (context.allowReturnTypes(this)) {
     final Ref<? extends PyType> yieldTypeRef = getYieldStatementType(context);
     if (yieldTypeRef != null) {
       return yieldTypeRef.get();
     }
     return getReturnStatementType(context);
   }
   return null;
 }
 @Nullable
 private PyType getGenericReturnType(
     @NotNull TypeEvalContext typeEvalContext, @Nullable PyQualifiedExpression callSite) {
   if (typeEvalContext.maySwitchToAST(this)
       && LanguageLevel.forElement(this).isAtLeast(LanguageLevel.PYTHON30)) {
     PyAnnotation anno = getAnnotation();
     if (anno != null) {
       PyClass pyClass = anno.resolveToClass();
       if (pyClass != null) {
         return new PyClassTypeImpl(pyClass, false);
       }
     }
   }
   for (PyTypeProvider typeProvider : Extensions.getExtensions(PyTypeProvider.EP_NAME)) {
     final PyType returnType = typeProvider.getReturnType(this, callSite, typeEvalContext);
     if (returnType != null) {
       returnType.assertValid(typeProvider.toString());
       return returnType;
     }
   }
   final PyType docStringType = getReturnTypeFromDocString();
   if (docStringType != null) {
     docStringType.assertValid("from docstring");
     return docStringType;
   }
   if (typeEvalContext.allowReturnTypes(this)) {
     final PyType yieldType = getYieldStatementType(typeEvalContext);
     if (yieldType != null) {
       return yieldType;
     }
     return getReturnStatementType(typeEvalContext);
   }
   return null;
 }
  /**
   * Adds type and description representation from function docstring
   *
   * @param parameter parameter of a function
   * @return true if type from docstring was added
   */
  private boolean addTypeAndDescriptionFromDocstring(@NotNull final PyNamedParameter parameter) {
    final PyFunction function = PsiTreeUtil.getParentOfType(parameter, PyFunction.class);
    if (function != null) {
      final String docString = PyPsiUtils.strValue(function.getDocStringExpression());
      final Pair<String, String> typeAndDescr = getTypeAndDescription(docString, parameter);

      final String type = typeAndDescr.first;
      final String description = typeAndDescr.second;

      if (type != null) {
        final PyType pyType = PyTypeParser.getTypeByName(parameter, type);
        if (pyType instanceof PyClassType) {
          myBody
              .addItem(": ")
              .addWith(
                  new LinkWrapper(PythonDocumentationProvider.LINK_TYPE_PARAM),
                  $(pyType.getName()));
        } else {
          myBody.addItem(": ").addItem(type);
        }
      }

      if (description != null) {
        myEpilog.addItem(BR).addItem(description);
      }

      return type != null;
    }

    return false;
  }
 @Nullable
 private static PyType derefType(
     @NotNull Ref<PyType> typeRef, @NotNull PyTypeProvider typeProvider) {
   final PyType type = typeRef.get();
   if (type != null) {
     type.assertValid(typeProvider.toString());
   }
   return type;
 }
 @Nullable
 @Override
 public PyType getCallType(
     @NotNull TypeEvalContext context, @NotNull PyQualifiedExpression callSite) {
   PyType type = null;
   for (PyTypeProvider typeProvider : Extensions.getExtensions(PyTypeProvider.EP_NAME)) {
     type = typeProvider.getCallType(this, callSite, context);
     if (type != null) {
       type.assertValid(typeProvider.toString());
       break;
     }
   }
   if (type == null) {
     type = context.getReturnType(this);
   }
   final PyTypeChecker.AnalyzeCallResults results =
       PyTypeChecker.analyzeCallSite(callSite, context);
   if (results != null) {
     return analyzeCallType(type, results.getReceiver(), results.getArguments(), context);
   }
   return type;
 }
 @Nullable
 @Override
 public PyType getCallType(
     @NotNull TypeEvalContext context, @NotNull PyCallSiteExpression callSite) {
   for (PyTypeProvider typeProvider : Extensions.getExtensions(PyTypeProvider.EP_NAME)) {
     final PyType type = typeProvider.getCallType(this, callSite, context);
     if (type != null) {
       type.assertValid(typeProvider.toString());
       return type;
     }
   }
   final PyExpression receiver = PyTypeChecker.getReceiver(callSite, this);
   final List<PyExpression> arguments = PyTypeChecker.getArguments(callSite, this);
   final List<PyParameter> parameters = PyUtil.getParameters(this, context);
   final PyResolveContext resolveContext =
       PyResolveContext.noImplicits().withTypeEvalContext(context);
   final List<PyParameter> explicitParameters =
       PyTypeChecker.filterExplicitParameters(parameters, this, callSite, resolveContext);
   final Map<PyExpression, PyNamedParameter> mapping =
       PyCallExpressionHelper.mapArguments(arguments, explicitParameters);
   return getCallType(receiver, mapping, context);
 }
    @Nullable
    @Override
    public ParseResult fun(@NotNull Pair<Token<PyElementType>, List<Token<PyElementType>>> value) {
      final Token<PyElementType> first = value.getFirst();
      final List<Token<PyElementType>> rest = value.getSecond();
      final TextRange firstRange = first.getRange();
      final boolean unqualified = rest.isEmpty();

      if (unqualified) {
        final ParseResult result = parseBuiltinType(first);
        if (result != null) {
          return result;
        }
      }

      final PsiFile file = myAnchor.getContainingFile();
      final List<Token<PyElementType>> tokens = new ArrayList<>();
      tokens.add(first);
      tokens.addAll(rest);

      if (file instanceof PyFile) {
        final PyFile pyFile = (PyFile) file;
        final TypeEvalContext context = TypeEvalContext.codeInsightFallback(file.getProject());
        final Map<TextRange, PyType> types = new HashMap<>();
        final Map<PyType, TextRange> fullRanges = new HashMap<>();
        final Map<PyType, PyImportElement> imports = new HashMap<>();

        PyType type = resolveQualifierType(tokens, pyFile, context, types, fullRanges, imports);
        PsiElement resolved = type != null ? getElement(type) : null;

        if (type != null) {
          final PyResolveContext resolveContext =
              PyResolveContext.defaultContext().withTypeEvalContext(context);
          final PyExpression expression =
              myAnchor instanceof PyExpression ? (PyExpression) myAnchor : null;

          for (Token<PyElementType> token : tokens) {
            final PyType qualifierType = type;
            type = null;
            final List<? extends RatedResolveResult> results =
                qualifierType.resolveMember(
                    token.getText().toString(), expression, AccessDirection.READ, resolveContext);
            if (results != null && !results.isEmpty()) {
              resolved = results.get(0).getElement();
              if (resolved instanceof PyTypedElement) {
                type = context.getType((PyTypedElement) resolved);
                if (type != null && !allowResolveToType(type)) {
                  type = null;
                  break;
                }
                if (type instanceof PyClassLikeType) {
                  type = ((PyClassLikeType) type).toInstance();
                }
              }
            }
            if (type == null) {
              break;
            }
            types.put(token.getRange(), type);
            fullRanges.put(
                type,
                TextRange.create(firstRange.getStartOffset(), token.getRange().getEndOffset()));
          }
          if (type != null) {
            return new ParseResult(resolved, type, types, fullRanges, imports);
          }
        }
      }

      return EMPTY_RESULT;
    }