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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 set_start_time(self, start):
 """Sets the assessment start time. arg: start (osid.calendaring.DateTime):
 assessment start time raise: InvalidArgument - ``start`` is invalid raise: NoAccess - ``Metadata.isReadOnly()`` is ``true`` *compliance: mandatory -- This method must be implemented.* """

        # Implemented from template for osid.assessment.AssessmentOfferedForm.set_start_time_template
        if self.get_start_time_metadata().is_read_only():
            raise errors.NoAccess()
        if not self._is_valid_date_time(
                start,
                self.get_start_time_metadata()):
            raise errors.InvalidArgument()
        self._my_map['startTime'] = start