A Python script to invert a mapping spreadsheet. This will be useful for mapping VegBank to VegX, so that we can just run the invert map script to get the reverse mapping.

The following transformations are needed:

1. swap the columns
2. remove input create-only attributes (:[...])
3. expand input split paths to separate input paths, each mapping to the same output
4. remove duplicate occurrences of the same input with different _alt ranks by choosing the best rank
5. remove input _alt ranks