Returns the attribute specified by the fqdn list from obj.

def _obj_getattr(obj, fqdn, start=1):
    """Returns the attribute specified by the fqdn list from obj.
    """
    node = obj
    for chain in fqdn.split('.')[start:]:
        if hasattr(node, chain):
            node = getattr(node, chain)
        else:
            node = None
            break
    return node