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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def gen_cmd_and_param_completions(self):
 """ generates command and parameter completions """

        if self.complete_command:
            for param in self.command_param_info.get(self.current_command, []):
                if self.validate_param_completion(param, self.leftover_args):
                    yield self.yield_param_completion(param, self.unfinished_word)
        elif not self.leftover_args:
            for child_command in self.subtree.children:
                if self.validate_completion(child_command):
                    yield Completion(child_command, -len(self.unfinished_word))