title: Python documentation style for instances of class vs class objects
body: <p>What is the standard way to document the type of function arguments and class attributes to differentiate between those that are expected to be instances of a class and those that are expected to be class objects themselves?</p>
  
  <pre><code>class TestClass(object):
      def __init__(self):
          pass
  
  class Objectify(object):
      def __init__(self):
          pass    
  
  class NeatDocumentation(object):
      """A class demonstrating neat documentation style.
  
      Attributes:
          cls (TestClass?): A class you want to test.
          obj (Objectify?): An instance of `Objectify` class.
          string (str): A string because why not.
      """
  
      def __init__(self, cls_, obj, string):
          self.cls = cls_  # An instance can be created by executing self.cls()
          self.obj = obj
          self.string = string
  </code></pre>