human
Solve the following python programming problem given the following code:
def add_source_code_and_doc(f) : 
    'Instrospects the function and adds source code and the doc string to 
    the return parameters.
    ' 
    @ wraps (f) 
    def f_with_source_and_doc(request, title, sidebar_items, * args, **kwargs) : 
        doc = f.__doc__ 
        if (doc is None) : 
            doc = '' 
else : 
            doc = textwrap.dedent (f.__doc__) 
(src_lines, num_lines) = inspect.getsourcelines (f) 
        start_line = end_line = None 
        for (i, line) in enumerate (src_lines) : 
            if ((start_line is None) or (end_line is None)) : 
                if ('#start_code' in line) : 
                    start_line = (i + 1) 
if ('#end_code' in line) : 
                    end_line = i 
else : 
                break 
if (end_line is None) : 
            end_line = (num_lines - 1) 
if (start_line is None) : 
            start_line = 1 
code = ''.join (src_lines [start_line : end_line]) 
        code = textwrap.dedent (code) 
        return f (request, code = code, title = title, doc = doc, sidebar_items = sidebar_items) 
return <MASK> 
    
    Given the code above, what is a proper replacement for <MASK>?
assistant
#Here is a proper replacement for <MASK>.
def f_with_source_and_doc(