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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_lowest_numeric_score(self):
 """Gets the lowest number in a numeric grading system. return: (decimal) - the lowest number raise: IllegalState - ``is_based_on_grades()`` is ``true`` *compliance: mandatory -- This method must be implemented.* """

        if self.is_based_on_grades():
            raise errors.IllegalState('This GradeSystem is based on grades')
        if self._my_map['lowestNumericScore'] is None:
            return None
        else:
            return Decimal(str(self._my_map['lowestNumericScore']))