how to set the contrast group with normal vs tumor for what i want, not default

[honghh2018]

Hi,
in my case, i want to set the contrast direct for normal vs tumor not the reverse for below code:
DA_results <- testNhoods(milo_sce2, design = ~ tissue, design.df = design_df2)
design_df2 the data.frame look like below:

how to specific the contrast direct ?
any advice would be appreciated,
Best,
hanhuihong

[honghh2018]

Had anyone hear this issue?

[MikeDMorgan]

Refer to the vignette on setting contrasts: https://www.bioconductor.org/packages/release/bioc/vignettes/miloR/inst/doc/milo_contrasts.html