Unit test for the single speed/stage IEER calculation (#103)

* DX_system_added_1_HL

* update DX more 2

* update DX system;test get_ref_values() function

* ieer added; i/o process added

* check ieer cal

* update format with black

* correct Generator in tests

* correct using black again

* correct generator import again

* update generator again

* update based on comments

* reformat

* correct import

* correct another problem

* update another round

* update format

* add tests, correct ieer issue

* correct format

* correct test

* update 04262024

* error with arg check

* update previous problems

* update 05062024

* 05062024 update 2

* update model check

* new unittests and json file DX

* fix comment problems

* update 340/360

* format

* update

* update

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Co-authored-by: Wan <hanlong.wan@pnnl.gov>