Refactor argument handling: simplify logic by using arg_len variable

[kaz2700]

Provide an overview of the implemented solution or the fix and elaborate on the modifications.

Refactored the argument handling logic in the simulation code. Introduced a variable arg_len to simplify the checks on the length of args and reduce redundancy. The new structure first checks the length of args and branches accordingly to call the appropriate simulation methods (_simulate_power_law, _simulate_model, _simulate_model_string, _simulate_power_spectrum, or _simulate_impulse_response) based on the type and number of arguments passed.

Is there a new dependency introduced by your contribution? If so, please specify.

No new dependencies have been introduced.

Any other comments?

This refactor improves the readability and maintainability of the code.