title: VSCode, Python3.7: pylint no-member error with custom decorated class
body: <p>I have recently moved an instance method out of its class definition and put is as a global function (in example: deco_function) to be able to use it in different classes again. See the following code for detailed explanation and bug reproduction:</p>
  <pre><code>def deco_function(cls):
      
      def inner_fct(self):
          print('do something')
  
      cls.deco_function = inner_fct
      return cls
  
  @deco_function
  class Something:
  
      def __init__(self):
          print('init')
          self.deco_function()
          print('done')
  
  if __name__ == '__main__':
      a = Something()
  </code></pre>
  <p>The code runs completely fine, printing</p>
  <pre><code>init
  do something
  done
  </code></pre>
  <p>however, VSCode underlines <code>self.deco_function()</code> red, with pylint stating, that Instance 'Something' has no 'deco_function' member.</p>
  <p>Is there a way around, preventing pylint from marking this or making VSCode recognize deco_function as an Instance member?</p>
  <p>Thanks for any advice.</p>