Constant EDGE_TOOLTIP_CSS 

pub(crate) const EDGE_TOOLTIP_CSS: &str = r#"
.edge-hover .edge-tooltip {
  opacity: 0;
  pointer-events: none;
  transition: opacity 120ms ease-out;
}
.edge-hover:hover .edge-tooltip {
  opacity: 1;
}
.edge-hover .edge-hover-point {
  opacity: 0.65;
  pointer-events: none;
  transition: opacity 120ms ease-out;
}
.edge-hover:hover .edge-hover-point {
  opacity: 0.95;
}
"#;