title: Python mock call_args_list unpacking tuples for assertion on arguments
body: <p>I'm having some trouble dealing with the nested tuple which <code>Mock.call_args_list</code> returns.</p>
  
  <pre><code>def test_foo(self):
      def foo(fn):
          fn('PASS and some other stuff')
  
      f = Mock()
      foo(f)
      foo(f)
      foo(f)
  
      for call in f.call_args_list:
          for args in call:
              for arg in args:
                  self.assertTrue(arg.startswith('PASS'))
  </code></pre>
  
  <p>I would like to know if there is a better way to unpack that call_args_list on the mock object in order to make my assertion. This loop works, but it feels like there must be a more straight forward way.</p>