From docs@python.org:

"""
In a number of places we find documentation with optional leading arguments where the meta-notation (square brackets) are in the wrong place.   For example, for range, the standard doc heading says

       range([start], stop [, step])   # The comma after start should be inside the square bracket, not outside.

The same error occurs with docs for print, and for slice, for random.randrange and for random.seed, etc, etc.   This seems a consistent bug whenever a function or method takes an optional first argument, and it looks like it might have been put there by some tool that generates the docs.

I use Python 3 - perhaps there was once a time when one had to supply the comma if one omitted the first argument?   In Python 3 it gives errors if one follows the documentation carefully and uses the comma.
""""

(or see http://mail.python.org/pipermail/docs/2012-August/010051.html )