Application.nargs should be a tuple in all cases (issue 3741)
Canonicalize nargs (to be a tuple) in Function class
Implement some suggestions on PR#2201
Modify Function classes (nargs: int -> tuple)
Fix tests
Revert "Modify Function classes (nargs: int -> tuple)"

This reverts commit 9528e8917ab5cf2c675403204fb9219102bc5cf2.