public int getColumnCount() {
		if (verticesByColumn.isEmpty()) {
			return 0;
		}
		Integer largestColumn = verticesByColumn.lastKey();
		Integer smallestColumn = verticesByColumn.firstKey();
		int diff = Math.abs(largestColumn - smallestColumn); // abs for negative column values
		return diff + 1; // +1 for zero-based values
	}
Represents the range of columns in this row.  For this given row in a grid:
<pre>
	0 1 2 3 4 5 6
	- - v - v - - 
</pre>
the column count is 3--where the column range is 2-4, inclusive.   

<p>Note: this differs from then number of vertices in this row, as the column count
includes columns that have no vertex.

@return the number of columns in this row, including empty columns between start and end
Ghidra/Framework/Graph/src/main/java/ghidra/graph/viewer/layout/Row.java