code: function (time /* ms */, props) {
          var tracks = this._tracks;
          for (var propName in props) {
              if (!props.hasOwnProperty(propName)) {
                  continue;
              }
  
              if (!tracks[propName]) {
                  tracks[propName] = [];
                  // Invalid value
                  var value = this._getter(this._target, propName);
                  if (value == null) {
                      // zrLog('Invalid property ' + propName);
                      continue;
                  }
                  // If time is 0
                  //  Then props is given initialize value
                  // Else
                  //  Initialize value from current prop value
                  if (time !== 0) {
                      tracks[propName].push({
                          time: 0,
                          value: cloneValue(value)
                      });
                  }
              }
              tracks[propName].push({
                  time: time,
                  value: props[propName]
              });
          }
          return this;
      }
docs: 设置动画关键帧
  @param  {number} time 关键帧时间，单位是ms
  @param  {Object} props 关键帧的属性值，key-value表示
  @return {module:zrender/animation/Animator}