NET_VOLUME: IndicatorDescriptor = ...

Net Volume: the bar's own volume, signed by the direction its close took.

There is no warmup gap. Bar 0 has no previous close, so neither the up test nor the down test can hold and the reference falls through to its zero arm; an unchanged close lands on that same arm later in the series. Blanking bar 0 instead would put a hole in a series that is defined on every other bar.