title: Can you annotate return type when value is instance of cls?
body: <p>Given a class with a helper method for initialization:</p>
  
  <pre><code>class TrivialClass:
      def __init__(self, str_arg: str):
          self.string_attribute = str_arg
  
      @classmethod
      def from_int(cls, int_arg: int) -&gt; ?:
          str_arg = str(int_arg)
          return cls(str_arg)
  </code></pre>
  
  <p>Is it possible to annotate the return type of the <code>from_int</code> method?</p>
  
  <p>I'v tried both <code>cls</code> and <code>TrivialClass</code> but PyCharm flags them as unresolved references which sounds reasonable at that point in time.</p>