How to use the nanopb.nanopb.generator.nanopb_generator.ExtensionRange function in nanopb

continue

            field = Field(self.name, f, field_options)
            if (hasattr(f, 'oneof_index') and
                f.HasField('oneof_index') and
                f.oneof_index not in no_unions):
                if f.oneof_index in self.oneofs:
                    self.oneofs[f.oneof_index].add_field(field)
            else:
                self.fields.append(field)

        if len(desc.extension_range) > 0:
            field_options = get_nanopb_suboptions(desc, message_options, self.name + 'extensions')
            range_start = min([r.start for r in desc.extension_range])
            if field_options.type != nanopb_pb2.FT_IGNORE:
                self.fields.append(ExtensionRange(self.name, range_start, field_options))

        self.packed = message_options.packed_struct
        self.ordered_fields = self.fields[:]
        self.ordered_fields.sort()