def add_docs_for(other_func):

    def dec(func):
        func.__doc__ = other_func.__doc__ + '\n\n' + func.__doc__
return func
return dec

def foo():
    """documentation for foo"""
pass

@add_docs_for(foo)
def bar():
    """additional notes for bar"""
pass
help(bar)
Работа со строками в строках документации Python