code: def is_a_Builder(obj):
      Returns True if the specified obj is one of our Builder classes.
  
      The test is complicated a bit by the fact that CompositeBuilder
      is a proxy, not a subclass of BuilderBase.
      """
      return (isinstance(obj, BuilderBase)
              or isinstance(obj, CompositeBuilder)
              or callable(obj))
docs: Returns True if the specified obj is one of our Builder classes.
  
      The test is complicated a bit by the fact that CompositeBuilder
      is a proxy, not a subclass of BuilderBase.