Changed EMMO representation of function arguments from datasets to datum

[jesper-friis]

Description

Changed EMMO representation of function arguments from datasets to datum.

Type of change

• Bug fix and code cleanup
• New feature
• Documentation update
• Testing

Checklist for the reviewer

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?
• Is the code properly tested?

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 78.42%. Comparing base (36dd746) to head (2707285).

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #203   +/-   ##
=======================================
  Coverage   78.42%   78.42%           
=======================================
  Files          18       18           
  Lines        1650     1650           
=======================================
  Hits         1294     1294           
  Misses        356      356           

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[francescalb]

Good, but be aware that this migt be a breaking change for some. Should there be a release in advance?