Implement Espirit sensitivity estimation

[georgeyiasemis]

Implements Espirit calibration sensitivity map estimation and methods to calculate maximum eigenvalue numerically (e.g. powermethod)

[codecov]

Codecov Report

Base: 83.55% // Head: 83.88% // Increases project coverage by +0.32% 🎉

Coverage data is based on head (8d26336) compared to base (5bda5c5).
Patch coverage: 98.01% of modified lines in pull request are covered.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #233      +/-   ##
==========================================
+ Coverage   83.55%   83.88%   +0.32%     
==========================================
  Files          88       91       +3     
  Lines        6001     6136     +135     
==========================================
+ Hits         5014     5147     +133     
- Misses        987      989       +2     

Impacted Files	Coverage Δ
direct/algorithms/optimization.py	92.68% <92.68%> (ø)
direct/algorithms/__init__.py	100.00% <100.00%> (ø)
direct/algorithms/mri_algorithms.py	100.00% <100.00%> (ø)
direct/data/mri_transforms.py	97.15% <100.00%> (+0.14%)	⬆️
direct/data/transforms.py	96.47% <100.00%> (+0.16%)	⬆️
direct/types.py	83.33% <100.00%> (+5.55%)	⬆️

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

☔ View full report at Codecov.
📢 Do you have feedback about the report comment? Let us know in this issue.

[jonasteuwen]

Only a few remarks

• Perhaps all should derived from Algorithm?
• Use abc for abstract classes
• Implement .fit(), don't use __call__() for this behaviour.

[jonasteuwen]

LGTM