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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def rationalize_file(item_f, charset, mode='rb', lock=False):
    '''FSQ attempts to treat all file-like things as line-buffered as an
       optimization to the average case.  rationalize_file will handle file
       objects, buffers, raw file-descriptors, sockets, and string
       file-addresses, and will return a file object that can be safely closed
       in FSQ scope without closing the file in the bounding caller.'''
    # file, TmpFile, socket, etc ...
    if hasattr(item_f, 'fileno'):
        n_fd = os.dup(item_f.fileno())
        try:
            _lock(n_fd, lock)
            # explicitily decrement file ref
            del item_f
            return os.fdopen(n_fd)
        except Exception, e:
            os.close(n_fd)
            raise e

    # StringIO, cStringIO, etc ...
    elif hasattr(item_f, 'readline'):
        return item_f
    # raw file descriptor -- e.g. output of pipe
    elif isinstance(item_f, numbers.Integral):
        n_fd = os.dup(item_f)
        try:
            _lock(n_fd, lock)
            return os.fdopen(n_fd)
        except Exception, e:
            os.close(n_fd)
            raise e

    # try to open, read+binary, line-buffered
    f = open(coerce_unicode(item_f, charset), mode, 1)
    try:
        _lock(f.fileno(), lock)
        return f
    except Exception, e:
        f.close()
        raise e