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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 diff(self, first_row: List[Row], second_row: List[Row], column: NumberColumn) -> Number: """ Takes a two rows and a number column and returns the difference between the values under that column in those two rows. """

        if not first_row or not second_row:
            return 0.0  # type: ignore
        first_value = first_row[0].values[column.name]
        second_value = second_row[0].values[column.name]
        if isinstance(first_value, float) and isinstance(second_value, float):
            return first_value - second_value  # type: ignore
        else:
            raise ExecutionError(f"Invalid column for diff: {column.name}")