ICD-10 only (see flag_suicide_types). Warns if an explicit pre-1999 `year` is supplied.
Examples
df <- data.frame(ucod = c("X60", "X64", "X72"))
flag_suicide_poison(df)
#> ucod suicide_poison
#> 1 X60 1
#> 2 X64 1
#> 3 X72 0