Draft: Add max_col to sheet parsing
Take max_col into account before parsing a row. This code speeds up this code path; I added a test case and a test spreadsheet for illustration. That test case is timing-dependent, so likely shouldn't be merged as is.
There's another performance issue iterating through self.source, here. For the MaxColsDT.xlsx spreadsheet, the source has ~2.5million elements, of which <100 were relevant. This iteration was taking about half the total time of the parse iteration before I added max_col. I'm not sure how to solve this issue. Maybe there's some pre-filtering that can be done?
--HG-- branch : 3.2