'Should the drop event be accepted?'

def acceptsDropEvent(self, event):

    if ((event.source() is not None) and (event.source().window() is not self.window())):
        return False
    mime = event.mimeData()
    vars = mime.property('_items')
    if (vars is None):
        return False
    if (not all((isinstance(var, self.__acceptedType) for var in vars))):
        return False
    event.accept()
    return True
