code: function (otherStyle, overwrite) {
          if (otherStyle) {
              for (var name in otherStyle) {
                  if (otherStyle.hasOwnProperty(name)
                      && (overwrite === true
                          || (
                              overwrite === false
                                  ? !this.hasOwnProperty(name)
                                  : otherStyle[name] != null
                          )
                      )
                  ) {
                      this[name] = otherStyle[name];
                  }
              }
          }
      }
docs: Extend from other style
  @param {zrender/graphic/Style} otherStyle
  @param {boolean} overwrite true: overwrirte any way.
  false: overwrite only when !target.hasOwnProperty
  others: overwrite when property is not null/undefined.