Switched MGCycle to sg by default

[ewu63]

Purpose

Closes #191. I was thinking about actually listing out the possible choices for this option, but a quick glance at the Fortran code shows that this may be a bit complicated to do. Maybe the current description is okay.

Expected time until merged

Should be pretty quick.

Type of change

• Bugfix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (non-backwards-compatible fix or feature)
• Code style update (formatting, renaming)
• Refactoring (no functional changes, no API changes)
• Documentation update
• Maintenance update
• Other (please describe)

Testing

None

Checklist

• I have run flake8 and black to make sure the code adheres to PEP-8 and is consistently formatted
• I have run unit and regression tests which pass locally with my changes
• I have added new tests that prove my fix is effective or that my feature works
• I have added necessary documentation

[codecov]

Codecov Report

Merging #212 (d8a76c6) into main (0a9fe1b) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #212   +/-   ##
=======================================
  Coverage   43.32%   43.32%           
=======================================
  Files          15       15           
  Lines        3550     3550           
=======================================
  Hits         1538     1538           
  Misses       2012     2012           

Impacted Files	Coverage Δ
adflow/pyADflow.py	67.45% <ø> (ø)

📣 Codecov can now indicate which changes are the most critical in Pull Requests. Learn more

[marcomangano]

I am fine with having just this change for now, maybe we could look deeper into the options as we deal with #206 ?

[sseraj]

We can't put all possible options into a list, but we could be more clear that the input is an integer specifying the number of grid levels and then w or v specifying the type of cycle. We also have the option to manually describe a cycle with a sequence of 0, -1, 1 but I don't know if anyone uses that.