tgp_silk_road_movement_stream_effect

tgp_silk_road_movement_stream_effect = {
	$SUB_REGION$ ?= {
		save_temporary_scope_as = sub_region_temp
		var:innovation ?= { save_temporary_scope_as = old_innovation_temp }
	}
	$UPSTREAM_SUB_REGION$ = {
		save_temporary_scope_as = upstream_sub_region_temp
		var:innovation ?= { save_temporary_scope_as = new_innovation_temp }
	}
	scope:sub_region_temp = {
		every_player = {
			limit = {
				save_temporary_scope_as = player_temp
				scope:sub_region_temp = { any_situation_sub_region_participant = { this = scope:player_temp } }
			}
			send_interface_message = {
				type = msg_silk_road_innovation_movement
				title = msg_silk_road_innovation_movement_stream_title
				desc = msg_silk_road_innovation_movement_stream_desc
				custom_tooltip = msg_silk_road_innovation_movement_tt
			}
		}
		set_variable = {
			name = innovation
			value = scope:new_innovation_temp
		}
	}
}

As written in game/common/scripted_effects/10_dlc_tgp_silk_road_scripted_effects.txt.