Language reference/ Expressions/ Evaluation order
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In the following lines, expressions will be evaluated in the arithmetic
order of their suffixes:
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func(expr1, expr2, *expr3, **expr4)

The omission of a suffix from the function expression could imply that
such are somehow not included in the left-to-right rule.  Suggest
'func0', 'f_expr0', 'func_expr0' or just 'expr0' possibly renumbered from 1.

expr1(expr2, expr3, *expr4, **expr5)
is probably most consistent with other examples.