<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _reset_values(self, instance):
 """Reset all associated values and clean up dictionary items"""

        self.value = None
        self.reference.value = None
        instance.__dict__.pop(self.field_name, None)
        instance.__dict__.pop(self.reference.field_name, None)
        self.reference.delete_cached_value(instance)