'Returns the name of the extension that virtualEvent is bound in, or
None if not bound in any extension.
virtualEvent - string, name of the virtual event to test for, without
the enclosing \'<< >>\''

def GetExtnNameForEvent(self, virtualEvent):

    extName = None
    vEvent = (('<<' + virtualEvent) + '>>')
    for extn in self.GetExtensions(active_only=0):
        for event in self.GetExtensionKeys(extn).keys():
            if (event == vEvent):
                extName = extn
    return extName
