<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _massage_metakeys(dct, prfx):
 """ Returns a copy of the supplied dictionary, prefixing any keys that do not begin with the specified prefix accordingly. """

    lowprefix = prfx.lower()
    ret = {}
    for k, v in list(dct.items()):
        if not k.lower().startswith(lowprefix):
            k = "%s%s" % (prfx, k)
        ret[k] = v
    return ret