human
I wrote the below code

    def expand(arg):
        for (k, v) in arg.items():
            for item in as_list(v):
                (yield ('%s:%s' % (k, item)))
    if isinstance(arg, dict):
        return '|'.join(sorted(expand(arg)))
    raise TypeError(('Expected    a    dict    for    components,    but    got    %s' % type(arg).__name__))

What's a good function header?
assistant
#Here's a good function header.

def components(arg):