code: def DeregisterDefinition(self, data_type_definition):
      
      name = data_type_definition.name.lower()
      if name not in self._definitions:
        raise KeyError('Definition not set for name: {0:s}.'.format(
            data_type_definition.name))
  
      del self._definitions[name]
docs: Deregisters a data type definition.
  
      The data type definitions are identified based on their lower case name.
  
      Args:
        data_type_definition (DataTypeDefinition): data type definition.
  
      Raises:
        KeyError: if a data type definition is not set for the corresponding
            name.