ENH: On Demand Imports

[John-P]

The aim of this PR (which is a branch off of tidying wsireader.py) aims to make imports only happen as needed where possible. This means that some dependencies can be avoided if they are not required.

On demand imports so far:

• glymur (and openjpeg)
• defusedxml

[John-P]

@ghadjigeorghiou For a minimal set of requirements, I believe you could skip these:

• jupyterlab
• sphinx (we should probably remove this from requirements.txt as it's only needed for dev and docs builds)
• glymur and openjpeg (if not using JP2)
• defusedxml if not using TIFFWSIReader (OME)

Other libraries which could fairly easily be made to be imported on demand if desired:

• albumentions
• umap-learn
• matplotlib
• flask
• shapely

[codecov]

Codecov Report

Merging #222 (2925edb) into develop (c56b5dc) will increase coverage by 0.00%.
The diff coverage is 100.00%.

@@           Coverage Diff            @@
##           develop     #222   +/-   ##
========================================
  Coverage    99.81%   99.81%           
========================================
  Files           53       53           
  Lines         4869     4870    +1     
  Branches       800      800           
========================================
+ Hits          4860     4861    +1     
  Misses           2        2           
  Partials         7        7           

Impacted Files	Coverage Δ
tiatoolbox/wsicore/wsireader.py	99.12% <100.00%> (+<0.01%)	⬆️

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[John-P]

I may leave this a just glymur / openjpeg for now, as that makes another non-pip dependency optional, which is nice.

[shaneahmed]

Thanks @John-P