Polar selectors: one per series, which is what a line-shaped layer needs.
LineTrace pairs its series with its selectors by position, so a single
selector covering the whole layer would resolve to nothing on a chart with
more than one series. Plotly gives every scatter group a trace{uid}
compound class, so each series can be named directly; barpolar's groups
carry no uid and are counted within the subplot's g.barlayer instead.
A uid that is not a usable class name — plotly generates safe ones, but an
author may set uid to anything — withdraws the whole list rather than
emitting a selector that would silently match nothing.
Polar selectors: one per series, which is what a line-shaped layer needs.
LineTracepairs its series with its selectors by position, so a single selector covering the whole layer would resolve to nothing on a chart with more than one series. Plotly gives every scatter group atrace{uid}compound class, so each series can be named directly; barpolar's groups carry no uid and are counted within the subplot'sg.barlayerinstead.A uid that is not a usable class name — plotly generates safe ones, but an author may set
uidto anything — withdraws the whole list rather than emitting a selector that would silently match nothing.