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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 query_uast(self, query, query_col='uast', output_col='result'):
 """ Queries the UAST of a file with the given query to get specific nodes. :param query: xpath query :type query: str :param query_col: column containing the list of nodes to query :type query_col: str :param output_col: column to place the result of the query :type output_col: str :rtype: UASTsDataFrame """

        return UASTsDataFrame(self._engine_dataframe.queryUAST(query,
                                       query_col,
                                       output_col),
                              self._session, self._implicits)