'Get maximum clearsnippets priority without arguments for specified
filetypes, if any.
It returns None if there are no clearsnippets.'

def get_clear_priority(self, filetypes):

    pri = None
    for ft in self._get_existing_deep_extends(filetypes):
        snippets = self._snippets[ft]
        if ((pri is None) or (snippets._clear_priority > pri)):
            pri = snippets._clear_priority
    return pri
