Calculates at which level the data are coming from in each plot.
fortify_filled_trait(object, other_col_how, ...)filled traits from trait_fill().
what to do with the other columns in other data.
Options are to filter by one of the columns, add them to the x-axis,
facet by them, or to ignore.
optional filters for use with other_col_how = "filter"
a tibble