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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 get_data(self, file_id):
 """ Acquires the data from the table identified by the id. The file is read only once, consecutive calls to this method will return the sale collection. :param file_id: identifier for the table :return: all the values from the table """

        if file_id not in self._file_values:
            file_contents = 'cwr_%s.csv' % file_id
            self._file_values[file_id] = self._reader.read_csv_file(
                file_contents)

        return self._file_values[file_id]