def METHOD_NAME(string, shared_secret, challenge_hmac):
    """
    Verify a challenging hmac signature against a string / shared-secret for
    github webhooks.
    .. versionadded:: 2017.7.0
    Returns a boolean if the verification succeeded or failed.
    CLI Example:
    .. code-block:: bash
        salt '*' hashutil.github_signature '{"ref":....} ' 'shared secret' 'sha1=bc6550fc290acf5b42283fa8deaf55cea0f8c206'
    """
    msg = string
    key = shared_secret
    hashtype, challenge = challenge_hmac.split("=")
    if isinstance(msg, str):
        msg = salt.utils.stringutils.to_bytes(msg)
    if isinstance(key, str):
        key = salt.utils.stringutils.to_bytes(key)
    hmac_hash = hmac.new(key, msg, getattr(hashlib, hashtype))
    return hmac_hash.hexdigest() == challenge