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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_completion(self, completion):
 """Sets the completion percentage. arg: completion (decimal):
 the completion percentage raise: InvalidArgument - ``completion`` is invalid raise: NoAccess - ``Metadata.isReadOnly()`` is ``true`` *compliance: mandatory -- This method must be implemented.* """

        # Implemented from template for osid.grading.GradeSystemForm.set_lowest_numeric_score
        if self.get_completion_metadata().is_read_only():
            raise errors.NoAccess()
        try:
            completion = float(completion)
        except ValueError:
            raise errors.InvalidArgument()
        if not self._is_valid_decimal(completion, self.get_completion_metadata()):
            raise errors.InvalidArgument()
        self._my_map['completion'] = completion