Add Start End Events

Prepend a path_start and append a path_end synthetic event to each path.

Idempotent: a path that already starts or ends with these events is left unchanged on that side.

You normally don't need to call this directly — transition_graph, step_matrix, and step_sankey insert path_start/path_end themselves, each using its own path_col. Calling this upfront bakes in one specific path definition and can produce misleading boundaries if a widget is later given a different path_col.

Usage

stream.add_start_end_events()

Parameters