Parameter get renamed in compound model

Presumably for @embray or @nden: If I make a composition of two models which have a parameter `a` and parameter `b` respectively. These get then translated into `a_0` and `b_1`. Is there any way to avoid this.

No file, test, or entry point is named. Reproduce the reported composition of two models with parameters a and b, inspect how the resulting a_0 and b_1 names are assigned, and define done as a documented or tested way to retain the original names if supported.

Written by the indexing model from the issue text.