Problem

Currently the tripcolor function accepts only Normalize objects and None for the norm argument. However, the underlying functions used by tripcolor all seem to accept a string value for norm such as log, symlog, etc.

I therefore suggest permitting the passing of string values for the norm argument in tripcolor.

Proposed solution

I suggest changing the line

_api.check_isinstance((Normalize, None), norm=norm)

in tripcolor to

_api.check_isinstance((Normalize, str, None), norm=norm)

I have tested this change with both gouraud and flat values passed as the shading argument and, as far as I can tell, it works perfectly.