Fix accessing concepts via secondary category

[patrickkwang]

Fixes #181.

[codecov]

Codecov Report

Merging #188 (e1e1f2e) into master (9905697) will decrease coverage by 0.55%.
The diff coverage is n/a.

❗ Current head e1e1f2e differs from pull request most recent head 6401681. Consider uploading reports for the commit 6401681 to get more accurate results

@@            Coverage Diff             @@
##           master     #188      +/-   ##
==========================================
- Coverage   81.95%   81.39%   -0.56%     
==========================================
  Files          15       15              
  Lines        1236     1172      -64     
==========================================
- Hits         1013      954      -59     
+ Misses        223      218       -5     

Impacted Files	Coverage Δ
icees_api/features/knowledgegraph.py	85.94% <ø> (-0.23%)	⬇️
icees_api/handlers.py	77.56% <0.00%> (-2.75%)	⬇️
icees_api/trapi.py	90.00% <0.00%> (-0.63%)	⬇️
icees_api/app.py	92.77% <0.00%> (-0.09%)	⬇️
icees_api/features/mappings.py	100.00% <0.00%> (ø)

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[hyi]

This PR does not apply any more due to removal of knowledgegraph.py as part of moving to ICEES KG cleanup, so closing the PR.