code: function(sym) {
          var css = null;
          for(var prop in this.cssMap) {
              if(this.cssMap[prop] == sym) {
                  css = prop;
                  break;
              }
          }
          return css;
      }
docs: Method: getCssProperty
  Given a symbolizer property, get the corresponding CSS property
  from the <cssMap>.
  
  Parameters:
  sym - {String} A symbolizer property name.
  
  Returns:
  {String} A CSS property name or null if none found.