old_contents: from .explanation import Explanation
  
  
  def explain(
      predicate,
      code='valid',
      message_valid='data is valid',
      message_invalid='data is not valid',
      details_valid=None,
      details_invalid=None,
  ):
      """
      Wraps a predicate with an explanation. You can set the explanation messages
      with the parameters ``explanation_valid`` and ``explanation_invalid``.
  
      This method is also very nice way to use predicates from other sources than
      `Is Valid?` that don't have an ``explain`` parameter to work with
      explanations.
      """
      return lambda data, explain=False: (
          Explanation(True, code, message_valid, details_valid)
          if predicate(data) else
          Explanation(False, 'not_' + code, message_invalid, details_invalid)
      ) if explain else predicate(data)
  
  
  class Wrapper:
  
      def __init__(self, func=None):
          self.func = func
      
      def __call__(self, *args, **kwargs):
          if self.func is None:
              raise AttributeError('Wrapper has no function.')
          return self.func(*args, **kwargs)
new_contents: from .explanation import Explanation
  
  
  def explain(
      predicate,
      code='valid',
      message_valid='data is valid',
      message_invalid='data is not valid',
      details_valid=None,
      details_invalid=None,
  ):
      """
      Wraps a predicate with an explanation. You can set the explanation messages
      with the parameters ``explanation_valid`` and ``explanation_invalid``.
  
      This method is also very nice way to use predicates from other sources than
      `Is Valid?` that don't have an ``explain`` parameter to work with
      explanations.
      """
      return lambda data, explain=False: (
          Explanation(True, code, message_valid, details_valid)
          if predicate(data) else
          Explanation(False, 'not_' + code, message_invalid, details_invalid)
      ) if explain else predicate(data)
  
  
  class Wrapper:
  
      def __init__(self, func=None):
          self.func = func
  
      def __call__(self, *args, **kwargs):
          if self.func is None:
              raise AttributeError('Wrapper has no function.')
          return self.func(*args, **kwargs)
  
subject: Fix linting errors.