docs: def parse_boolean(value):
      """
      Coerce a value to boolean.
  
      :param value: the value, could be a string, boolean, or None
      :return: the value as coerced to a boolean
      """
  
      if value is None:
          return None
  
      if isinstance(value, bool):
          return value
  
      if isinstance(value, string_types):
          value = value.lower()
          if value == 'false':
              return False
          if value == 'true':
              return True
  
      raise ValueError("Could not convert value to boolean: {}".format(value))