code: function iterateStyleRules(argument) {
        if (typeof argument === 'string') {
          checkStyleExistence(styleDefinitions, argument);
  
          collectedStyles.push(styleDefinitions[argument]);
          return;
        }
  
        if (typeof argument === 'object') {
          Object.keys(argument).forEach(function(styleName) {
            checkStyleExistence(styleDefinitions, styleName);
  
            if (argument[styleName]) {
              collectedStyles.push(styleDefinitions[styleName])
            }
          })
        }
      }
docs: Iterate passed style rules and build style collection based on it.