renameAttrs option no longer works

I'm coming back to CycleJS and JSX-Transform after some break.
Versions and APIs of both changed quite a bit 😄

I discovered that renameAttrs option no longer works.
It is undocumented (why?) but still present in source code.

This JSX transform options:

let jsxOptions = {
  factory: "Cycle.h",
  renameAttrs: {
    "class": "className",
  }
};

now produces this invalid VirtualDOM code:

Cycle.h('input', {class: "myinput", type: "text"})

instead of expected:

Cycle.h('input', {className: "myinput", type: "text"})

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