Corrected get_by_label to use only labels in the ontology #1818

Job	Run time
EMMO documentation (test using ontodoc)	3m 1s
pytest (3.7)	3m 38s
pytest (3.8)	3m 52s
pytest (3.9)	3m 47s
pytest (3.10)	3m 57s
pytest (3.11)	3m 51s
External / Build distribution package	25s
External / Build Documentation	1m 0s
External / Run `pre-commit`	1m 19s
External / Run `pylint` & `safety`	1m 12s
	26m 2s

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