<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def add_composition(self, composition):
 """Add a composition to the suite. Raise an UnexpectedObjectError when the supplied argument is not a Composition object. """

        if not hasattr(composition, 'tracks'):
            raise UnexpectedObjectError("Object '%s' not expected. Expecting "
                    "a mingus.containers.Composition object." % composition)
        self.compositions.append(composition)
        return self