'Toggle tools, need to untoggle prior to using other Toggle tool
Called from trigger_tool
Parameters
tool: Tool object
sender: object
Object that wishes to trigger the tool
canvasevent : Event
Original Canvas event or None
data : Object
Extra data to pass to the tool when triggering'

def _handle_toggle(self, tool, sender, canvasevent, data):

    radio_group = tool.radio_group
    if (radio_group is None):
        if (tool.name in self._toggled[None]):
            self._toggled[None].remove(tool.name)
        else:
            self._toggled[None].add(tool.name)
        return
    if (self._toggled[radio_group] == tool.name):
        toggled = None
    elif (self._toggled[radio_group] is None):
        toggled = tool.name
    else:
        self.trigger_tool(self._toggled[radio_group], self, canvasevent, data)
        toggled = tool.name
    self._toggled[radio_group] = toggled
