old_contents: """A collection of classes, which can check table rows for conditions."""
  
  
  class Condition:
      """Base class for all condition checks."""
      pass
  
  
  class OneOf(Condition):
      """Class for checking, if a certain field in part of a list of items."""
  
      def __init__(self, field, lst):
          """Store field name and list of items in object."""
          self._field = field
          self._lst = lst
  
      def __call__(self, compare):
          """Check, if the item compare holds the object condition."""
          return getattr(compare, self._field) in self._lst
  
  
  class Equal(OneOf):
      """Class for checking, if a certain field is equal to a value."""
  
      def __init__(self, field, equal):
          super().__init__(field, [equal])
  
  
  class DNF(Condition):
      """Class for checking, if a certain field is / is not a DNF."""
  
      def __init__(self, field, dnf=True):
          """Store field name and list of items in object."""
          self._field = field
          self._dnf = dnf
  
      def __call__(self, compare):
          """Check, if the item compare holds the object condition."""
          return (getattr(compare, self._field) != -1) == self._dnf
  
new_contents: """A collection of classes, which can check table rows for conditions."""
  
  
  class Condition:
      """Base class for all condition checks."""
      pass
  
  
  class OneOf(Condition):
      """Class for checking, if a certain field in part of a list of items."""
  
      def __init__(self, field, lst):
          """Store field name and list of items in object."""
          self._field = field
          self._lst = lst
  
      def __call__(self, compare):
          """Check, if the item compare holds the object condition."""
          return getattr(compare, self._field) in self._lst
  
  
  class Equal(OneOf):
      """Class for checking, if a certain field is equal to a value."""
  
      def __init__(self, field, equal):
          super().__init__(field, [equal])
  
  
  class DNF(Condition):
      """Class for checking, if a certain field is / is not a DNF."""
  
      def __init__(self, field, dnf=True):
          """Store field name and list of items in object."""
          self._field = field
          self._dnf = dnf
  
      def __call__(self, compare):
          """Check, if the item compare holds the object condition."""
          return (getattr(compare, self._field) == -1) == self._dnf
  
subject: fix dnf condition (dnf=false means removing dnfs)