def _webwallet_support(coin, support):
    """Check the "webwallet" support property.
    If set, check that at least one of the backends run on trezor.io.
    If yes, assume we support the coin in our wallet.
    Otherwise it's probably working with a custom backend, which means don't
    link to our wallet.
    """
    if not support.get("webwallet"):
        return False
    return any(".trezor.io" in url for url in coin["blockbook"] + coin["bitcore"])