class_docstr: Problem spec for English-Setswana translation.
  
  Uses the RMA Autshumato dataset.
code: def approx_vocab_size(self):
      return 2**15
  
file_path: tensor2tensor/tensor2tensor/data_generators/translate_entn.py
imports: from tensor2tensor.data_generators import problem
  from tensor2tensor.data_generators import text_encoder
  from tensor2tensor.data_generators import translate
  from tensor2tensor.utils import registry
label_desc: Use image node_id 1 for calling the TranslateEntnRma obj's underlying member method code with example usage: obj.approx_vocab_size() and returns: unknown