code: function findFirstSubNodeLTR (node, type) {
    if (!node || !node.children) return null
    for (let i = 0; i < node.children.length; ++i) {
      var item = node.children[i]
      if (nodeType(item, type)) return item
      else {
        var res = findFirstSubNodeLTR(item, type)
        if (res) return res
      }
    }
    return null
  }
docs: Finds first node of a certain type under a specific node.
  @node {AstNode} node to start form
  @type {String} Type the ast node should have
  @return {AstNode} null or node found