Check if object is a grouped tidymatrix
Examples
library(dplyr, warn.conflicts = FALSE)
tm <- tidymatrix(big5_responses, big5_respondents, big5_items)
is_grouped_tidymatrix(tm)
#> [1] FALSE
is_grouped_tidymatrix(tm |> activate(rows) |> group_by(country))
#> [1] TRUE