old_contents: 
  class Constellation(object):
      """Manage and analyze data from multiple pysat Instruments.
  
      FIXME document this.
      """
      def __init__(self, instruments=None, name=None):
          if instruments and name:
              raise ValueError('When creating a constellation, please specify a '
                               'list of instruments or a name, not both.')
          elif instruments and not hasattr(instruments, '__getitem__'):
              raise ValueError('Constellation: Instruments must be list-like.')
          elif not (name or instruments):
              raise ValueError('Constellation: Cannot create empty constellation.')
  
          if instruments:
              self.instruments = instruments
          else:
              # TODO Implement constellation lookup by name.
              raise NotImplementedError()
  
      def __getitem__(self, *args, **kwargs):
          return self.instruments.__getitem__(*args, **kwargs)
  
      def __str__(self):
          # TODO Implement conversion to string.
          raise NotImplementedError()
  
      def __repr__(self):
          # TODO Implement __repr__
          raise NotImplementedError()
  
      def add(self, bounds1, label1, bounds2, label2, bin3, label3,
              data_label):
          # TODO Implement signal addition.
          raise NotImplementedError()
  
      def difference(self, instrument1, instrumet2, data_labels):
          # TODO Implement signal difference.
          raise NotImplementedError()
  
new_contents: 
  class Constellation(object):
      """Manage and analyze data from multiple pysat Instruments.
  
      FIXME document this.
      """
      def __init__(self, instruments=None, name=None):
          if instruments and name:
              raise ValueError('When creating a constellation, please specify '
                               'a list of instruments or a name, not both.')
          elif instruments and not hasattr(instruments, '__getitem__'):
              raise ValueError('Constellation: Instruments must be list-like.')
          elif not (name or instruments):
              raise ValueError('Constellation: Cannot create empty '
                               'constellation.')
  
          if instruments:
              self.instruments = instruments
          else:
              # TODO Implement constellation lookup by name.
              raise NotImplementedError()
  
      def __getitem__(self, *args, **kwargs):
          return self.instruments.__getitem__(*args, **kwargs)
  
      def __str__(self):
          # TODO Implement conversion to string.
          raise NotImplementedError()
  
      def __repr__(self):
          # TODO Implement __repr__
          raise NotImplementedError()
  
      def add(self, bounds1, label1, bounds2, label2, bin3, label3,
              data_label):
          # TODO Implement signal addition.
          raise NotImplementedError()
  
      def difference(self, instrument1, instrumet2, data_labels):
          # TODO Implement signal difference.
          raise NotImplementedError()
  
subject: Change line wrap to appease pycodestyle.