code: function processBreakpoint(root, breakpointOption) {
    if (breakpointOption && breakpointOption !== Object(breakpointOption)) {
      throw new Error('Breakpoint must be of type Object.');
    }
  
    const processedBreakpoint = Object.assign({}, breakpointOption);
  
    let atRule;
    /* search current rules to see if one exists */
    root.walkAtRules('media', rule => {
      if (rule.params !== processedBreakpoint.mediaQuery) return;
      atRule = rule;
    });
  
    /* if no rules exist, create a new one */
    if (!atRule) {
      atRule = postcss.atRule({
        name: 'media',
        params: processedBreakpoint.mediaQuery,
      });
    }
  
    processedBreakpoint.atRule = atRule;
    return processedBreakpoint;
  }
docs: Processes a breakpoint option by creating a PostCSS @media atRule from the options
  @param {Object} root Root postcss node
  @param {Object} breakpointOption
  @param {String} breakpointOption.name
  @param {String} breakpointOption.mediaQuery
  @return {Object} Processed breakpoint option