Gets the grade in this entry if the grading system is based on grades.

        return: (osid.grading.Grade) - the grade
        raise:  IllegalState - ``is_graded()`` is ``false`` or
                ``GradeSystem.isBasedOnGrades()`` is ``false``
        raise:  OperationFailed - unable to complete request
        *compliance: mandatory -- This method must be implemented.*

def get_grade(self):
        """Gets the grade in this entry if the grading system is based on grades.

        return: (osid.grading.Grade) - the grade
        raise:  IllegalState - ``is_graded()`` is ``false`` or
                ``GradeSystem.isBasedOnGrades()`` is ``false``
        raise:  OperationFailed - unable to complete request
        *compliance: mandatory -- This method must be implemented.*

        """
        grade_system = self.get_gradebook_column().get_grade_system()

        for grade in grade_system.get_grades():
            if str(grade.ident) == self._my_map['gradeId']:
                return grade
        raise errors.IllegalState('gradeId does not exist in this GradeSystem')