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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def annotate_proto(self, text, annotators=None):
 """Return a Document protocol buffer from the CoreNLP server, containing annotations of the text. :param (str) text: text to be annotated :param (list[str]) annotators: a list of annotator names :return (CoreNLP_pb2.Document):
 a Document protocol buffer """

        properties = {
            'annotators': ','.join(annotators or self.default_annotators),
            'outputFormat': 'serialized',
            'serializer': 'edu.stanford.nlp.pipeline.ProtobufAnnotationSerializer'
        }
        r = self._request(text, properties)
        buffer = r.content  # bytes

        size, pos = _DecodeVarint(buffer, 0)
        buffer = buffer[pos:(pos + size)]
        doc = CoreNLP_pb2.Document()
        doc.ParseFromString(buffer)
        return doc