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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 his_from_sql(self, db_name, point):
 """ Retrive point histories from SQL database """

        his = self._read_from_sql('select * from "%s"' % "history", db_name)
        his.index = his["index"].apply(Timestamp)
        return his.set_index("index")[point]