human
Complete this python program:
def IdentifiersConcat():
assistant
#Here is the Python program you requested.

    """String concatenation aggregator for the identifiers map
    """
    def step(ctxt, key, val):
        ctxt.append((u'%s:%s' % (key, val)))
    def finalize(ctxt):
        return u','.join(ctxt)
    return ([], step, finalize)