code: def add_capability(base, *classes):
      
      if _debug: add_capability._debug("add_capability %r %r", base, classes)
  
      # start out with a collector
      if not issubclass(base, Collector):
          raise TypeError("base must be a subclass of Collector")
  
      # make sure you only add capabilities
      for cls in classes:
          if not issubclass(cls, Capability):
              raise TypeError("%s is not a Capability subclass" % (cls,))
  
      base.__bases__ += classes
      for cls in classes:
          base.__name__ += '+' + cls.__name__
docs: Add capabilites to an existing base, all objects get the additional
      functionality, but don't get inited.  Use with great care!