@classmethod
def get_balance(cls, address):
    """Gets the balance of an address in satoshi.

        :param address: The address in question.
        :type address: ``str``
        :raises ConnectionError: If all API services fail.
        :rtype: ``int``
        """
    for api_call in cls.GET_BALANCE_MAIN:
        try:
            return api_call(address)
        except cls.IGNORED_ERRORS:
            pass
    raise ConnectionError('All APIs are unreachable.')
