it's to its

[svenstaro]

It's a possessive its.

[mattupstate]

Hate to tell you, but its is the possessive form. it's is a contraction for "it is".

[svenstaro]

Indeed, and I suppose the sentence is supposed to be

This function receives the token payload as its only positional argument

as opposed to

This function receives the token payload as it is only positional argument.

[mattupstate]

Oh dear. I'm a moron. I thought your pull request was the other way around!