docs: def get_source(self, key, name_spaces=None, default_prefix=''):
          """Generates the dictionary key for the serialized representation
          based on the instance variable source and a provided key.
  
          :param str key: name of the field in model
          :returns: self.source or key
          """
          source = self.source or key
          prefix = default_prefix
          if name_spaces and self.name_space and self.name_space in name_spaces:
              prefix = ''.join([name_spaces[self.name_space], ':'])
          return ''.join([prefix, source])