Currently, I just set them to [`one(pnsystem)`](https://github.com/moble/PostNewtonian.jl/blob/58b5981ef7b666c5e2a2e0c35a7c2f91ef647b1f/src/utilities/macros.jl#L105), but it's possible that subtypes might want to use specific values.
Currently, I just set them to
one(pnsystem), but it's possible that subtypes might want to use specific values.