Added multiply function and unit tests

[NimahMasuud]

• Implemented the multiply function to handle multiplication of two numbers with type validation.
• Added comprehensive unit tests for multiply function covering:
  • Positive and negative numbers
  • Zero multiplication
  • Floating-point numbers
  • Invalid inputs with error handling
• Applied Ruff linting to ensure code quality and PEP8 compliance.

[AhmadHamedDehzad]

My review and Observations
Code Quality
The multiply function is really easy to read and understand.
It has a docstring that explains what the function does, what the inputs are, what it returns, and even examples of how to use it. That’s really helpful for beginners like me!
The function checks if the inputs are numbers, which makes it safer to use because it raises an error if something invalid is passed.
Code Formatting
The code looks clean and follows Python's style rules (PEP 8). The indentation and spacing are good.
There is a line at the top, #!/usr/bin/env python3, which I learned makes the script run in different environments easily. That’s a nice touch!
Testing Coverage
The tests are really good because they check for a lot of different cases:
Positive and negative numbers
Multiplying with zero
Invalid inputs like strings or None
The unittest framework is used, which is great because it’s built into Python and doesn’t need extra setup.
I like how the tests use assertEqual to check if the function is doing the right thing.
What I Learned
Writing docstrings is really important for explaining the code, and examples in the docstring make it even better.
Using type hints like float and type checks like isinstance makes the function easier to understand and prevents errors.
Testing different kinds of inputs (positive, negative, zero, invalid) helps make the function more reliable.
Overall
The code is clean, well documented, and the tests are thorough. As a beginner, I found it easy to understand and learned some good coding practices from it. 😊