class_docstr: Teacher for the sentence choosing task.
  
  Turkers were instructed to choose the 'most interesting' sentence from a paragraph.
class_docstr_tok: ["Teacher","for","the","sentence","choosing","task",".","Turkers","were","instructed","to","choose","the","'most","interesting","'","sentence","from","a","paragraph","."]
code: def next_example(self):
      action, epoch_done = super().next_example()
      action.force_set(
          "label_candidates", list(action["label_candidates"])
      )
      if "" in action["label_candidates"]:
          action["label_candidates"].remove("")
      return action, epoch_done
  
imports: from parlai.core.teachers import FbDeprecatedDialogTeacher, FixedDialogTeacher
  from parlai.utils.io import PathManager
  from .build import build
  import copy
  import os
label_desc: Use image node_id 2 for calling the SentencechooseTeacher obj's underlying member method code with example usage: obj.next_example() and returns: action,  epoch_done