code: func (c *chainView) NodeByHeight(height int32) *blockNode {
  	c.mtx.Lock()
  	node := c.nodeByHeight(height)
  	c.mtx.Unlock()
  	return node
  }
docs: // NodeByHeight returns the block node at the specified height.  Nil will be
  // returned if the height does not exist.
  //
  // This function is safe for concurrent access.