private void addColSegment(ColumnSegment<E> colSegment) {
		int col = colSegment.getCol();
		ColSegmentList<E> edgeCol =
			colSegmentMap.computeIfAbsent(col, k -> new ColSegmentList<E>(k));
		edgeCol.addSegment(colSegment);
	}
Finds the column segment object for the given edge and start point.
@param edge the edge for which to find its column segment object
@param gridPoint the start point for the desired segment object
@return the column segment object for the given edge and start point.
Ghidra/Features/FunctionGraph/src/main/java/ghidra/app/plugin/core/functiongraph/graph/layout/flowchart/EdgeSegmentMap.java