public void performOperation(String key, ParseFieldOperation operation) {
// if field already exist, remove field and any pending operation for that field
if (has(key)) {
operations.remove(key);
data.remove(key);
}
Object value = operation.apply(null, this, key);
if (value != null) {
data.put(key, value);
} else {
data.remove(key);
}
operations.put(key, operation);
dirtyKeys.add(key);
isDirty = true;
}
