code: def gen_masked_tree(self, node, mask_token, depth=1):
      actual_str_len = len(node.flat_str().strip().split(" "))
      return " ".join([mask_token for idx in range(actual_str_len)])
  
imports: from typing import Dict, List, Optional, Set
  import numpy
  from pytext.common.constants import SpecialTokens, Token
  from pytext.config.component import Component, ComponentType
  from pytext.config.pytext_config import ConfigBase
  from pytext.data.data_structures.annotation import Annotation, Intent, Root, Slot
  from pytext.data.utils import VocabBuilder, Vocabulary
label_desc: Use image node_id 1 for calling the MaskEverything obj's underlying member method code with example usage: obj.gen_masked_tree(node, mask_token, depth) and returns: str