def read_unexpandedDescriptors(current_key, json_flat):
    """
    Reading unexpandedDescriptors in BUFR file.

    unecpandedDescriptor contains the information which
    bufr messages are included in the message
    """
    descriptors = []
    i = int(current_key)
    while True:
        try:
            _ = json_flat['{0:07g}_value'.format(i)]
            break
        except KeyError:
            try:
                descriptors.append(json_flat['{0:07g}_'.format(i)])
                i += 1
            except KeyError:
                break
    return descriptors
