Companion packages implement methods for legacy or domain-specific objects.
The generic is owned by fmridataset so conversions have one canonical
destination and do not introduce competing frame classes.
Examples
src <- memory_source(matrix(seq_len(6), nrow = 2))
obs <- tibble::tibble(.obs_id = c("o1", "o2"))
fr <- fmri_frame(list(beta = src), obs)
identical(as_fmri_frame(fr), fr)
#> [1] TRUE