parameters: (self, field_name)
docstring: Checks if a certain field is set for the message. Note if the
      field_name is not defined in the message descriptor, ValueError will be
      raised.
docstring_summary: Checks if a certain field is set for the message. Note if the
      field_name is not defined in the message descriptor, ValueError will be
      raised.
docstring_tokens: Checks if a certain field is set for the message . Note if the field_name is not defined in the message descriptor ValueError will be raised .
function: def HasField(self, field_name):
      """Checks if a certain field is set for the message. Note if the
      field_name is not defined in the message descriptor, ValueError will be
      raised."""
      raise NotImplementedError
function_tokens: def HasField ( self , field_name ) : raise NotImplementedError