code: function getAllChildSpans(node) {
    return (
      Array.isArray(node.children)
        ? node.children
            .map(n => (n.spans || []).concat(getAllChildSpans(n)))
            .reduce((all, arr) => all.concat(arr))
        : []
    );
  }
docs: Returns all children of the provided node, including those that are descendents of the node's
  children.
  
  @param  {Node}   node
  @return {Span[]}