class_docstr: SwitchOut.
  :cite:`DBLP:journals/corr/abs-1808-07512`
docstr: Override this method to inform it need vocab to start.
docstr_tok: ["Override","this","method","to","inform","it","need","vocab","to","start","."]
code: def require_vocab(cls):
      """Override this method to inform it need vocab to start."""
      return True
  
imports: import random
  import numpy
  from onmt.constants import DefaultTokens
  from onmt.transforms import register_transform
  from .transform import Transform, ObservableStats
label_desc: Use image node_id 2 for calling the SwitchOutTransform obj's underlying member method code with example usage: obj.require_vocab(cls) and returns: True