The core function of this functionality is retrieve_exposure_entities_data_units_types(), defined in readers.py. It is called by main() in gdeimporter.py, where the output is printed to screen.
The configuration parameters are defined in config.yml and read with yaml in gdeimporter.py. The functions interpret_config_parameters() and interpret_potential_lists() aid in the interpretation of the configuration parameters.
The function retrieve_exposure_entities_data_units_types() is tested in tests/test_readers.py, using input files created for this purpose located in tests/data/.
\approve @fd
\fyi @ds