The parameters of the EDFA are explicitely retrieved in the EDFAParams class.
All the defaults are set instead in the gnpy.tool.json_io.AMP class.
Where required, the AMP.default_values are used instead of an empty dictionary.
Change-Id: Iba80a6a56bc89feb7e959b54b9bd424ec9b0bf06
Co-authored-by: Vittorio Gatto <vittoriogatto98@gmail.com>