Add support for hggoups. The code until now assumed that the parent of a graphics handle is an axes object. This is not true for more complex graphics object hierarchies (e.g. involving groups of handles by hggroups). Thus traverse the graphics tree upwards in case the parent is not an axes until the axes is finally found.
Add support for hggoups. The code until now assumed that the parent of a graphics handle is an axes object. This is not true for more complex graphics object hierarchies (e.g. involving groups of handles by hggroups). Thus traverse the graphics tree upwards in case the parent is not an axes until the axes is finally found.