public boolean containsEdge(E e) {
		return edgePoints.containsKey(e);
	}
Returns the minimum/max column for all rows in the grid. This method is only defined for
grids that have no negative rows. This is because the array returned will be 0 based, with
the entry at index 0 containing the column bounds for row 0 and so on.
@return the minimum/max column for all rows in the grid
@throws IllegalStateException if this method is called on a grid with negative rows.
Ghidra/Framework/Graph/src/main/java/ghidra/graph/viewer/layout/GridLocationMap.java