<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_unit_acceptable(self, unit, raise_exception=True):
 """Check if a certain unit is acceptable for the data type. Args: unit: A text string representing the abbreviated unit. raise_exception: Set to True to raise an exception if not acceptable. """

        _is_acceptable = unit in self.units

        if _is_acceptable or raise_exception is False:
            return _is_acceptable
        else:
            raise ValueError(
                '{0} is not an acceptable unit type for {1}. '
                'Choose from the following: {2}'.format(
                    unit, self.__class__.__name__, self.units
                )
            )