Fix Equality Testing for setProps

The previous equality testing did not catch undefined, this one makes
sure it is not null nor undefined (but only a function).

Author: Xing Han Lu

dash_cytoscape/Cytoscape.py

@@ -5,7 +5,8 @@
 
 class Cytoscape(Component):
     """A Cytoscape component.
-
+A Component Library for Dash aimed at facilitating network visualization in
+Python, wrapped around [Cytoscape.js](http://js.cytoscape.org/).
 
 Keyword arguments:
 - id (string; optional): The ID used to identify this component in Dash callbacks.