docs: def docstring(self, servicer):
          """Generate a doc-string."""
          s = getattr(servicer, to_lower_camel_case(self.name)).__doc__ \
              or "TODO: no docstring in .proto file"
  
          if self.uses_request:
              s += "\n"
              for field in get_fields(self.request_type):
                  if field != self.field_name:
                      type_info = get_field_description(
                          self.request_type.DESCRIPTOR.fields_by_name[field])
                      s += "    :param {}: {}\n".format(field, field)
                      s += "    :type {0}: {1}\n".format(field, type_info)
  
          return s