Some submodules don't show on ReadTheDocs

[zdelrosario]

The ReadTheDocs deployment doesn't show all submodules; for instance summarize. (NB this is from the source file summarize.py)

[mstites]

Working on this issue, and should have a PR out by the end of the summer research period.

Some notes so far (for documentation purposes):

• The only module actually missing readthedocs generation is grama.dfply. The ones that are missing use the @dfdelegate decorator, while ones that use the @make_symbolic decorator, or no decorator appear to be working in full. For example, when I changed "grama.dfply.join module" to use @make_symbolic the documentation generated.
• Continuing from the previous bullet, I noticed that the @dfdelegate decorator returns a "type: <class 'grama.dfply.base.group_delegation'>" while @make_symbolic still returns a "type: <class 'function'>". Forcing dfdelegate to return a function seems to fix the readthedocs issue. So the current challenge is figuring out a way for readthedocs to work with not a function, or for readthedocs for somehow otherwise getting the documentation issue.
• Another observation is that any missing code in a file will cause any following documentation pieces to not load. For example, if the module that is loaded before dfply (either by readthedocs itself, or by the grama import statements in grama/init.py, is missing or broken non of the dfply docs will load.
• There is a greater issue of docstrings not existing for user accessible functions. I will open a seperate issue for this.

I have learned all this by creating a more minimal py_grama branch, with just the items necessary for the dfply readthedocs page. While this code wouldn't work, this has been a useful troubleshooting tool for this issue - since pulling from readthedocs and sphinx documentation has been difficult to make progress.