<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 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