Model with EC SEI submodel takes long time to build

[valentinsulzer]

There is a parameter missing, so it is calling our (slow) implementation of the levenshtein ratio. Either speed up levenshtein ratio, or write the EC submodel in such a way that it does not need to call that (e.g. bypass the levenshtein ratio, which is only used for a nicer error message)

[valentinsulzer]

The problem is the try-except block in set_algebraic. Replacing with if ... in variables should be faster.