old_contents: import React from 'react';
  import cx from 'classnames';
  
  class CardPanel extends React.Component {
    render() {
      let classes = {
        'card-panel': true
      };
      let {className, children, ...props} = this.props;
      return (
        <div className={cx(classes, className)}>
          <span>{children}</span>
        </div>
      );
    }
  }
  
  export default CardPanel;
  
new_contents: import React from 'react';
  import cx from 'classnames';
  
  const CardPanel = ({
    className,
    children,
    ...props
  }) => {
    const classes = {
      'card-panel': true
    };
  
    return (
        <div className={cx(classes, className)}>
          <span>{children}</span>
        </div>
    );
  }
  
  export default CardPanel;
  
subject: Convert CardPanel to functional component