code: def onCall(self, n): #pylint: disable=invalid-name
          
          cond_oncall = n + 1
          return _SinonStubCondition(copy=self._copy, oncall=cond_oncall, cond_args=self._cond_args, cond_kwargs=self._cond_kwargs)
docs: Adds a condition for when the stub is called. When the condition is met, a special
          return value can be returned. Adds the specified call number into the condition
          list.
  
          For example, when the stub function is called the second time, it will return "#":
              stub.onCall(1).returns("#")
  
          Without returns/throws at the end of the chain of functions, nothing will happen.
          For example, in this case, although 2 is in the condition list, nothing will happen:
              stub.onCall(2)
  
          Args:
              n: integer, the call # for which we want a special return value.
                 The first call has an index of 0.
  
          Return:
              a SinonStub object (able to be chained)