code: function AbstractSyntaxTree(root, labels, manager) {
      this.root = root;
      this.labels = labels;
      this.manager = manager;
  
      manager.parse(this);
  }
docs: Represents a tree that can be executed
  
  @param {Array} root The root-level nodes
  @param {Object} labels An object of label: line mappings
  @param {BlockManager} manager The block manager