class_docstr: Validate input only when it appears in this list of sentences.
  
  :param sentences: List of sentences.
  :param ignore_case: If True, case-insensitive comparisons.
code: def validate(self, document):
      if document.text not in self.sentences:
          if self.move_cursor_to_end:
              index = len(document.text)
          else:
              index = 0
  
          raise ValidationError(
              cursor_position=index, message=self.error_message
          )
  
imports: from __future__ import unicode_literals
  from prompt_toolkit.validation import Validator, ValidationError
  from six import string_types
label_desc: Use image node_id 2 for calling the SentenceValidator obj's underlying member method code with example usage: obj.validate(document) without return types