code: function _convertTypeToD3Symbol(typeName) {
      switch (typeName) {
          case CONST.SYMBOLS.CIRCLE:
              return d3SymbolCircle;
          case CONST.SYMBOLS.CROSS:
              return d3SymbolCross;
          case CONST.SYMBOLS.DIAMOND:
              return d3SymbolDiamond;
          case CONST.SYMBOLS.SQUARE:
              return d3SymbolSquare;
          case CONST.SYMBOLS.STAR:
              return d3SymbolStar;
          case CONST.SYMBOLS.TRIANGLE:
              return d3SymbolTriangle;
          case CONST.SYMBOLS.WYE:
              return d3SymbolWye;
          default:
              return d3SymbolCircle;
      }
  }
docs: Converts a string that specifies a symbol into a concrete instance
  of d3 symbol.<br/>
  {@link https://github.com/d3/d3-shape/blob/master/README.md#symbol}
  @param  {string} typeName - the string that specifies the symbol type (should be one of {@link #node-symbol-type|node.symbolType}).
  @returns {Object} concrete instance of d3 symbol (defaults to circle).
  @memberof Node/helper