Increase code coverage

[SimonBin]

This is a general tracking issue which suggests to use pytest --cov or similar plus manual evaluation of the XML reports (eg. in PyCharm) to increase our test coverage

[alkidbaci]

---------- coverage: platform win32, python 3.9.12-final-0 -----------
Name                                                 Stmts   Miss  Cover
------------------------------------------------------------------------
ontolearn\__init__.py                                    2      0   100%
ontolearn\abstracts.py                                 283    129    54%
ontolearn\base_concept_learner.py                      208     16    92%
ontolearn\base_nces.py                                  77     60    22%
ontolearn\concept_generator.py                          88      0   100%
ontolearn\concept_learner.py                          1042    577    45%
ontolearn\core\__init__.py                               0      0   100%
ontolearn\core\owl\__init__.py                           0      0   100%
ontolearn\core\owl\hierarchy.py                        248     60    76%
ontolearn\core\owl\utils.py                            430     88    80%
ontolearn\data_struct.py                               154    122    21%
ontolearn\ea_algorithms.py                             152     74    51%
ontolearn\ea_initialization.py                         226     13    94%
ontolearn\ea_utils.py                                   86      5    94%
ontolearn\fitness_functions.py                          13      0   100%
ontolearn\heuristics.py                                 91     47    48%
ontolearn\knowledge_base.py                            363     40    89%
ontolearn\learning_problem.py                           33      2    94%
ontolearn\learning_problem_generator.py                241     79    67%
ontolearn\metrics.py                                    50     16    68%
ontolearn\model_adapter.py                             147     39    73%
ontolearn\nces_architectures.py                         72     62    14%
ontolearn\nces_modules.py                               53     37    30%
ontolearn\nces_trainer.py                              174    151    13%
ontolearn\nces_utils.py                                 24     13    46%
ontolearn\owlapy\__init__.py                             0      0   100%
ontolearn\owlapy\_utils.py                               7      0   100%
ontolearn\owlapy\ext\__init__.py                        32      4    88%
ontolearn\owlapy\fast_instance_checker.py              392     90    77%
ontolearn\owlapy\io.py                                  13      3    77%
ontolearn\owlapy\model\__init__.py                    1665    344    79%
ontolearn\owlapy\model\_base.py                         33     10    70%
ontolearn\owlapy\model\_iri.py                          83      6    93%
ontolearn\owlapy\model\providers.py                     37      3    92%
ontolearn\owlapy\namespaces.py                          29      4    86%
ontolearn\owlapy\owl2sparql\__init__.py                  0      0   100%
ontolearn\owlapy\owl2sparql\converter.py               367    130    65%
ontolearn\owlapy\owlready2\__init__.py                   4      0   100%
ontolearn\owlapy\owlready2\_base.py                    548     94    83%
ontolearn\owlapy\owlready2\axioms.py                   502    130    74%
ontolearn\owlapy\owlready2\complex_ce_instances.py      64     21    67%
ontolearn\owlapy\owlready2\utils.py                    265     21    92%
ontolearn\owlapy\parser.py                             365     17    95%
ontolearn\owlapy\render.py                             241     14    94%
ontolearn\owlapy\util.py                               336     22    93%
ontolearn\owlapy\vocab.py                               90      3    97%
ontolearn\refinement_operators.py                      580    111    81%
ontolearn\search.py                                    449    155    65%
ontolearn\utils\__init__.py                            124     89    28%
ontolearn\utils\log_config.py                           30     10    67%
ontolearn\utils\oplogging.py                             8      0   100%
tests\test_owlapy_cnf_dnf.py                            69      0   100%
tests\test_owlapy_fastinstancechecker.py               246      1    99%
tests\test_owlapy_nnf.py                               246      0   100%
tests\test_owlapy_owl2sparql_converter.py              197      5    97%
tests\test_owlapy_owlready2.py                         585      1    99%
tests\test_owlapy_parser.py                            345      0   100%
tests\test_owlapy_render.py                            132      1    99%
tests\test_refinement_operators.py                     205      1    99%
tests\test_value_splitter.py                            47      1    98%
------------------------------------------------------------------------
TOTAL                                                13524   2945    78%

After executing pytest --cov the above report was generated. @Demirrr you would probably like to see this.