Function column_classes 

pub fn column_classes(column: &Column<'_>, opts: &Emit) -> String

Every class a cell of this column carries.

The column’s own name, how wide it asks to be, when it drops, what it holds and its floor as a rung of the min-N ladder. A header cell has to carry the same classes or the header and the body disagree about which column just closed and how wide the rest are, and a renderer emitting its own header row should call this rather than assemble the list a second time.