code: def custom_handler(self, glade, function_name, widget_name, str1, str2, int1, int2):
          
          try:
              handler = getattr(self, function_name)
              return handler(str1, str2, int1, int2)
          except AttributeError:
              return None
docs: Generic handler for creating custom widgets, internally used to
          enable custom widgets (custom widgets of glade).
  
          The custom widgets have a creation function specified in design time.
          Those creation functions are always called with str1,str2,int1,int2 as
          arguments, that are values specified in design time.
  
          Methods of classes inheriting from SimpleGladeApp are used as
          creation functions automatically.
  
          If a custom widget has create_foo as creation function, then the
          method named create_foo is called with str1,str2,int1,int2 as arguments.