scFEA sampling and fitting function

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I have a large dataset of ~60,000 cells and it took me a long time to proceed. So I am considering breaking the large dataset into small groups based on cell types. Each cell type group would have two conditions: control and infection. Are the estimated cell-wise metabolic flux values within the same group directly comparable (i.e., I want to investigate how infection changes a specific metabolic reaction by comparing it to control cells)?

Where can I find the fitting function? As eventually I'd like to fit the estimated cell-wise metabolic flux values comparable among groups. Thanks!!