Upon further review and tests, I notice that ._decode
* is a partial implementation of Text.index,
* so it should be renamed index and tested against Text.index,
* and it currently returns the wrong values for 'end' and high out-of-bounds indexes.

Tests with 'end' only pass now because the tested methods ignore the buggy decode for 'end' and special-case it instead. When I added tests with out of bounds indexes, they failed. I am working now on fixing all this.

Spaces are supposed to follow arg-separating commas in function calls. The initial patch lacked them and I have added them. I need them because they make code easier for *me* to read and review, which is an example of why PEP-8 requires them.