Speed up and fix graph tests

[ethanwharris]

What does this PR do?

Fixes # (issue)

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[codecov]

Codecov Report

Merging #759 (6e8e614) into master (d963de7) will increase coverage by 1.12%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master     #759      +/-   ##
==========================================
+ Coverage   89.07%   90.20%   +1.12%     
==========================================
  Files         198      198              
  Lines       10693    10675      -18     
==========================================
+ Hits         9525     9629     +104     
+ Misses       1168     1046     -122     

Flag	Coverage Δ
unittests	90.20% <100.00%> (+1.12%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
flash/audio/classification/cli.py	100.00% <ø> (ø)
flash/audio/speech_recognition/cli.py	100.00% <ø> (ø)
flash/graph/classification/cli.py	92.30% <ø> (+49.45%)	⬆️
flash/image/classification/cli.py	84.61% <ø> (-1.10%)	⬇️
flash/image/classification/data.py	94.11% <ø> (ø)
flash/image/detection/cli.py	100.00% <ø> (ø)
flash/image/detection/data.py	93.75% <ø> (ø)
flash/image/instance_segmentation/cli.py	100.00% <ø> (ø)
flash/image/instance_segmentation/data.py	88.23% <ø> (ø)
flash/image/keypoint_detection/cli.py	100.00% <ø> (ø)
... and 31 more

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