title: python is instance() - how to make it worth with classes other than builtins
body: <p>Reading documentation for <code>isinstance()</code> and looking up examples online, examples only illustrate how to use it with builtin classes like: <code>str, int, float, long</code></p>
  
  <p>I have code where the variable <code>myObj.location</code> will either be <code>None</code> if it hasn't been set yet, be an empty <code>str</code> if the function fails to return a value, or if it succeeds, then the variable will hold an object of type: <code>geopy.location.Location</code></p>
  
  <p>To test what this object holds, I could write code like this:
  <code>isinstance(myObject.location, (type(None), str))</code></p>
  
  <p>If <code>False</code> then I know it failed to return the <code>Location</code> object.  If <code>True</code> then it either holds <code>None</code> or a <code>str</code>.</p>
  
  <p>Is there a way to tell it directly to test if the object is <code>geopy.location.Location</code> returning <code>True</code> if the test is right?</p>
  
  <p>My code works with the <code>False</code> test but I like the readability of being able to say <code>True</code> for an object of type <code>geopy.location.Location</code> that may or may not have been built for the first time at the moment of the <code>isinstance</code> test.</p>