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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 rpc_get_oneline_docstring(self, filename, source, offset):
 """Get a oneline docstring for the symbol at the offset. """

        return self._call_backend("rpc_get_oneline_docstring", None, filename,
                                  get_source(source), offset)