Update __main__.py (#99)

[etcart]

Class-Based Structure:
Introduced a MessageProcessor class to encapsulate related functionalities.

Error Handling:
    Used more structured error handling with specific exceptions (ValueError and Exception).

Command-Line Argument Handling:
    Checked the length of sys.argv before accessing sys.argv[1] to prevent an IndexError if the function name is not provided.

Readability:
    Added docstrings for functions and methods to improve documentation.

Consistency:
    Followed Python naming conventions more closely.

Simplified Logic:
    Simplified some parts of the logic for better readability.

[dragonked2]

Good