'Remove the specified child element or attribute.
@param child: A child to remove.
@type child: L{Element}|L{Attribute}
@return: The detached I{child} when I{child} is an element, else None.
@rtype: L{Element}|None'

def remove(self, child):

    if isinstance(child, Element):
        return child.detach()
    if isinstance(child, Attribute):
        self.attributes.remove(child)
    return None
