def parse_locator(src):
    """ (src:str) -> [pathfile:str, label:either(str, None)] 
    """
    pathfile_label = src.split('#')
    if len(pathfile_label)==1:
        pathfile_label.append(None)
    if len(pathfile_label)!=2:
        raise ValueError('Malformed src: %s' % (src))
    return pathfile_label