Returns the line in the CSS document where this section end.
The line number is 0-indexed, so the first line of the document will return 0. This value may change in future invocations of this function if
this is not yet parsed completely. This will for example happen in the GtkCssProvider:
GtkCssSection:parsing-error signal. The end position and line may be identical to the start position and line for sections which failed
to parse anything successfully.
the line number