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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def commandstr(command):
 """Convert command into string."""

    if command == CMD_MESSAGE_ERROR:
        msg = "CMD_MESSAGE_ERROR"
    elif command == CMD_MESSAGE_LIST:
        msg = "CMD_MESSAGE_LIST"
    elif command == CMD_MESSAGE_PASSWORD:
        msg = "CMD_MESSAGE_PASSWORD"
    elif command == CMD_MESSAGE_MP3:
        msg = "CMD_MESSAGE_MP3"
    elif command == CMD_MESSAGE_DELETE:
        msg = "CMD_MESSAGE_DELETE"
    elif command == CMD_MESSAGE_VERSION:
        msg = "CMD_MESSAGE_VERSION"
    elif command == CMD_MESSAGE_CDR_AVAILABLE:
        msg = "CMD_MESSAGE_CDR_AVAILABLE"
    elif command == CMD_MESSAGE_CDR:
        msg = "CMD_MESSAGE_CDR"
    else:
        msg = "CMD_MESSAGE_UNKNOWN"
    return msg