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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 _requirements(self):
 """ Gets a dictionary of all the object's resource requirements. Unset values are defaulted to None """

        return {'memory': getattr(self, 'memory', None),
                'cores': getattr(self, 'cores', None),
                'disk': getattr(self, 'disk', None),
                'preemptable': getattr(self, 'preemptable', None)}