why this code giving recursion error????

[נתי שטרן]

def compile(p, flags=0):
        # internal: convert pattern list to internal format

        if (isinstance(p,str)):
            pattern = p
            p = sre_parse.parse(p, flags)
        else:
            pattern = None

        code = _code(p, flags)

        if flags & SRE_FLAG_DEBUG:
            print()
            dis(code)

        # map in either direction
        groupindex = p.state.groupdict
        indexgroup = [None] * p.state.groups
        for k, i in groupindex.items():
            indexgroup[i] = k

        return sre_compile.compile(
            pattern, flags | p.state.flags, code,
            p.state.groups-1,
            groupindex, tuple(indexgroup)
        )


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