Converts given value to long if possible, otherwise None is returned.

        :param value:
        :return:

def field_to_long(value):
        """
        Converts given value to long if possible, otherwise None is returned.

        :param value:
        :return:
        """
        if isinstance(value, (int, long)):
            return long(value)
        elif isinstance(value, basestring):
            return bytes_to_long(from_hex(value))
        else:
            return None