@classmethod
def get_tx_amount(cls, txid, txindex):
    """Gets the ID of all transactions related to an address.

        :param txid: The transaction id in question.
        :type txid: ``str``
        :param txindex: The transaction index in question.
        :type txindex: ``str``
        :raises ConnectionError: If all API services fail.
        :rtype: ``list`` of ``str``
        """
    for api_call in cls.GET_TX_AMOUNT:
        try:
            return api_call(txid, txindex)
        except cls.IGNORED_ERRORS:
            pass
    raise ConnectionError('All APIs are unreachable.')
