[harmony] [docs] variables and subsetting

[JessicaS11]

We currently emphasize icepyx' ability to request variable-subsetted data because it can substantially decrease the file size. A non-exhaustive list of places we'll need to address this transition includes:

• docstrings
• general documentation
• examples: data access
• examples: variable subsetting
• other examples that link to the above

[betolink]

Looks like CMR has no way of listing variables by concept_id, this means that for now some methods will have to be either mocked/hard-coded or deprecated. e.g. region.order_vars.avail() what would be the preference here? cc @asteiker

[betolink]

Well there is something like this in

icepyx/icepyx/core/is2ref.py

Line 173 in 4eb7aaf

def _default_varlists(product):

but is not complete. Now since Harmony doesn't support variable subsetting, would it be useful to have a reference to them? all that customization has to go for now.

I'm going to focus on making this work:

import icepyx as ipx
import datetime as dt

q = ipx.Query(
    product="ATL06",
    version="006",
    spatial_extent=[-90, 68, 48, 90],
    date_range={
        "start_date": dt.datetime(2018, 10, 10, 0, 10, 0),
        "end_date": dt.datetime(2018, 10, 18, 14, 45, 30),
    }
)
q.submit_order()
q.download_granules("/tmp/atl06-order")

[JessicaS11]

mocked/hard-coded or deprecated. e.g. region.order_vars.avail()

My assumption was that Query.order_vars was one of the pieces that would be deprecated.

all that customization has to go for now.

Deprecating order_vars in Query should not impact the pieces of Variables management in is2ref.py and variables.py, which we will want to keep around (EDIT: I see now how changes in the CMR metadata that's available will impact this... I'm still exploring/learning given this realization). Those parts of the tooling are still used by read.py for users to specify which groups+variables they want to read in (since many users end up ordering data without variable subsetting, even if they used spatial and temporal subsetting since they're the defaults).

@betolink, I can put together a small PR that marks as deprecated some of these types of functions/properties in query.py. I've also been thinking about trying to type and update variables.py for the refactor. Would either of those be helpful for me to tackle next?