Dan,
Yes, the Predict Seagrass Habitats... module is what I'm working through, and I did find the thread you refer to prior to posting my question, but thanks anyway for sending it. In that case, the OP's question stemmed from naming an attribute 02 (with zero) instead of O2 (with letter O).
I'm having a different issue, with calling up the method, .as_matrix. I have since found this information, saying that as_matrix is no longer included in Python versions.
scikit learn - Python: Method .as_matrix will be removed in a future version. Use .values instead - ...
I think perhaps I need to learn how to replace as_matrix with .values() or .to_numpy() before I can proceed.
The deprecation of .values happened after the publication of the Seagrass module I'm trying to learn from.