La función help()

>>> help(print)
Help on built-in function print in module builtins:

print(...)
    print(value, ..., sep=' ', end='\n', file=sys.stdout, flush=False)

    Prints the values to a stream, or to sys.stdout by default.
[...]
>>> help(int)
Help on class int in module builtins:

class int(object)
 |  int(x=0) -> integer
 |  int(x, base=10) -> integer
 |
 |  Convert a number or string to an integer, or return 0 if no arguments
 |  are given.  If x is a number, return x.__int__().  For floating point
 |  numbers, this truncates towards zero.
[...]

class MiClase:
    """
    Esto será mostrado al llamar a help(MiClase).
    """
    
    def mi_funcion(self):
        """
        Esto, al llamar a help(MiClase.mi_funcion).
        """
        pass