Update assembly constraint docs

[lorenzncode]

• Correct FixedPoint constraint example
• Simplify Location usage in examples and format with black for consistency

[codecov]

Codecov Report

Merging #1210 (d71458a) into master (e23f43d) will increase coverage by 0.05%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1210      +/-   ##
==========================================
+ Coverage   94.01%   94.07%   +0.05%     
==========================================
  Files          26       26              
  Lines        5414     5414              
  Branches      919      919              
==========================================
+ Hits         5090     5093       +3     
+ Misses        193      190       -3     
  Partials      131      131              

Impacted Files	Coverage Δ
cadquery/cqgi.py	80.73% <0.00%> (+1.22%)	⬆️

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[lorenzncode]

Fixes #1159.

I removed a note on STEP and transparency. I find that STEP export includes transparency data so the note may be out of date.

[jmwright]

I created a test assembly with transparency and exported to STEP. Then I imported that into the online Autodesk viewer because the version of FreeCAD I'm running doesn't seem to respect the color info. Seems to confirm that transparency works.

[jmwright]

Thanks @lorenzncode !

[lorenzncode]

@jmwright Thanks for confirming transparency is working for you! Regarding colors, PR #1157 attempts to resolve an issue with STEP export and color handling. I've tested STEP export with the PR branch and several viewers, including FreeCAD and Autodesk, and did not find any problem. You might try exporting the STEP again with the PR 1157 branch to see if it resolves the color issue when viewing in FreeCAD.

[jmwright]

@lorenzncode I just tested in FreeCAD 0.20.1 and the color and alpha worked, but I had to turn off the STEP import option Enable STEP compound merge which is apparently on by default. If that setting is not turned off I get two default grey merged blocks.