如何使用Material-UI-React覆盖外部[第三方]组件的CSS？

import { makeStyles } from '@material-ui/core/styles';
import Button from '@material-ui/core/Button';

const useStyles = makeStyles((theme) => ({
  customButton: {
    // 添加自定义样式
    // ...
  },
}));

const MyComponent = () => {
  const classes = useStyles();

  return (
    <Button className={classes.customButton}>
      Custom Button
    </Button>
  );
};