code: def __parameter_default(self, field):
      
      if field.default:
        if isinstance(field, messages.EnumField):
          return field.default.name
        else:
          return field.default
docs: Returns default value of field if it has one.
  
      Args:
        field: A simple field.
  
      Returns:
        The default value of the field, if any exists, with the exception of an
            enum field, which will have its value cast to a string.