/**
  * Returns the CRS code for the specified envelope, or {@code null} if not found.
  *
  * @param envelope The envelope to return the CRS code.
  */
 public static String toCrsCode(final Envelope envelope) {
   if (org.geotoolkit.referencing.CRS.equalsIgnoreMetadata(
       envelope.getCoordinateReferenceSystem(), CommonCRS.WGS84.normalizedGeographic())) {
     return "EPSG:4326";
   }
   final Set<Identifier> identifiers = envelope.getCoordinateReferenceSystem().getIdentifiers();
   if (identifiers != null && !identifiers.isEmpty()) {
     return identifiers.iterator().next().toString();
   }
   return null;
 }
 public Resolution2154To4326Test()
     throws NoninvertibleTransformException, NoSuchAuthorityCodeException, FactoryException {
   super(CRS.forCode("EPSG:2154"), CommonCRS.WGS84.geographic(), new double[] {4300, 253}, 3);
 }