Add custom power and equation functions with counter

[elifyalvac]

Added custom power function and custom equation function with detailed docstring. Implemented a call counter function to track total calls and caller counts.

Describe your changes

Checklist

• [ X] I have read the [CONTRIBUTING]
• [ X] I have performed a self-review of my own code
• [ X] I have run the code locally and it works as expected
• [ X] I have commented my code, particularly in hard-to-understand areas

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