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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 prepare_query(self, symbol, start_date, end_date):
 """Method returns prepared request query for Yahoo YQL API."""

        query = \
            'select * from yahoo.finance.historicaldata where symbol = "%s" and startDate = "%s" and endDate = "%s"' \
            % (symbol, start_date, end_date)

        return query