docs: def expects_call(self):
          """The fake must be called.
  
          .. doctest::
              :hide:
  
              >>> import fudge
              >>> fudge.clear_expectations()
              >>> fudge.clear_calls()
  
          This is useful for when you stub out a function
          as opposed to a class.  For example::
  
              >>> import fudge
              >>> remove = fudge.Fake('os.remove').expects_call()
              >>> fudge.verify()
              Traceback (most recent call last):
              ...
              AssertionError: fake:os.remove() was not called
  
          .. doctest::
              :hide:
  
              >>> fudge.clear_expectations()
  
          """
          self._callable = ExpectedCall(self, call_name=self._name,
                                        callable=True)
          return self