You should never read the code to know what the library does.
That’s the job of the documentation or readme files, including docstrings.

Single-line Docstring

Quotations are on the same line.

def does_something(arg):
    """Takes one argument and does something to it based on type."""
    pass

Multi-line Docstring

The closing quotation is on a new line.

def does_something(arg):
    """Takes one argument and does something to it based on type.
    If arg is a string, returns arg * 3;
    If arg is an int or float, returns arg + 10
    """
    pass

Usage

>>> help(docstrings.does_something)
Takes one argument and does something to it based on type.
If arg is a string, returns arg * 3;
If arg is an int or float, returns arg + 10
Comment with Docstrings

You can use docstrings to comment multiple lines of code.
But that is NOT a recommended practice as it may lead to confusion.