Add Docs Based on ESDS Blog Posts

[mgrover1]

Toward #407

Include notebooks related to ESDS blog posts for documentation, including

• Derived Variable Functionality
• Building an Intake-ESM catalog from history files
• Creating visualizations of Intake-ESM catalogs
• Debugging the Intake-ESM process for reading in CMIP6 data

[andersy005]

Thank you for putting together, @mgrover1! I left a few comments... Once these are addressed, let's merge this!

• graphviz visualizaton notebook is broken
  • Add python-graphviz to the doc requirements
• derived variable notebook
  • Fix the missing data loading part. ds is used/mentioned without being defined. I presume ds is meant to the result of .to_dataset_dict().
  • Do you mind adding a section with a simple example that shows how to use DerivedVariableRegistry.load(....) to load a registry from a Python module? Here's an example from the unit tests:

    intake-esm/tests/test_derived.py

    Line 21 in e367251

    def test_registry_load():

[mgrover1]

@andersy005 - I added those missing/new sections you mentioned! When you get a chance, can you take a look and see if we can this merged soon?

[andersy005]

Thank you, Max!

The code for loading a registry from a Python module won't work unless you point it to a "valid" path. I don't think this has to be executable for demo purposes. How about making this code block non-executable by wrapping it in a markdown code block instead and mentioning that my_registry points to a Python module (my_registry.py) file which has to be on Python's sys.path

dvr = DerivedVariableRegistry.load('my_registry') # my_registry points to a Python module (`my_registry.py`) file which has to be on Python's `sys.path`

[andersy005]

Thank you, @mgrover1! I will ping you for reviews when the docs rearrangement is ready