_getTickLineProps() {
    const {
      tickSize,
      tickSizeOuter = tickSize,
      tickSizeInner = tickSize
    } = this.props;
    const isVertical = this._isAxisVertical();
    const tickXAttr = isVertical ? 'y' : 'x';
    const tickYAttr = isVertical ? 'x' : 'y';
    const wrap = this._areTicksWrapped() ? -1 : 1;
    return {
      [`${tickXAttr}1`]: 0,
      [`${tickXAttr}2`]: 0,
      [`${tickYAttr}1`]: -wrap * tickSizeInner,
      [`${tickYAttr}2`]: wrap * tickSizeOuter
    };
  }
Get the props of the tick line.
@returns {Object} Props.
@private