code: def spy(self):
          '''
          Add a spy to this stub. Return the spy.
          '''
          spy = Spy(self)
          self._expectations.append(spy)
          return spf spy(self):
          '''
          Add a spy to this stub. Return the spy.
          '''
          spy = Spy(self)
          self._expectations.append(spy)
          return spy
docs: Add a spy to this stub. Return the spy.