Update Docstrings to Follow NumPy Convention

[ldr426]

As @leewujung proposes in #122 (comment), we should update the docstrings in our project to adhere to the NumPy docstring convention. This will help improve consistency and readability in our documentation.

To avoid making this issue too large, I suggest creating a separate issue specifically for addressing the docstring convention. This can be tackled when we want to take a break from the histogram functionality.

Here's a suggested approach:

• Make all new docstrings in the histogram functionality PR in the numpy docstring style
• Create a separate PR for all other parts of the codebase to update their docstrings to the NumPy style convention.

Originally posted by @leewujung in #122 (comment)