Oxidation states in the oxoacids of sulphur

You will write functions that find the oxidation state of sulphur in an oxoacid, tell whether the acid has an O-O peroxide link, and list the acids that have a given state.

The idea. Oxygen is $-2$, except in an O-O link, where each oxygen atom is $-1$. Hydrogen is $+1$. The molecule is neutral, so the sulphur atoms must balance the rest.

Your tasks.

1. Complete oxidation_state(name) so that it returns the average oxidation state of sulphur.
2. Complete has_peroxo(name) so that it returns True when the acid has an O-O link.
3. Complete acids_with_state(state) so that it returns the list of acid names with that state, in the order of the table.