code: func assembleAttributeFactory(factory util.AttributeFactory,
  	clazz map[string]bool, ctor func() util.AttributeImpl) util.AttributeFactory {
  	return &myAttributeFactory{factory, clazz, ctor}
  }
docs: /*
  Returns an AttributeFactory returning an instance of the given clazz
  for the attributes it implements. The given clazz must have a public
  no-arg contructor. For all other attributes it calls the given
  delegate factory as fallback. This method can be used to prefer a
  specific AttributeImpl which combines multiple attributes over
  separate classes.
  
  Please save instances created by this method in a global field,
  because on each call, this does
  */