old_contents: '''Abstract base classes for fields and schemas.
  
  .. note::
  
     :mod:`lima.abc` is needed to avoid circular imports of fields needing to
     know about schemas and vice versa. The base classes are used for internal
     type checks. For users of the library there should be no need to use
     :mod:`lima.abc` directly.
  
  '''
  
  
  class FieldABC:
      '''Abstract base class for fields.
  
      Inheriting from :class:`FieldABC` marks a class as a field for internal
      type checks.
  
      (Usually, it's a *way* better Idea to subclass :class:`lima.fields.Field`
      directly)
  
      '''
      pass
  
  
  class SchemaABC:
      '''Abstract base class for schemas.
  
      Inheriting from :class:`SchemaABC` marks a class as a schema for internal
      type checks.
  
      (Usually, it's a *way* better Idea to subclass :class:`lima.schema.Schema`
      directly)
  
      '''
      pass
  
new_contents: '''Abstract base classes for fields and schemas.
  
  .. note::
  
     :mod:`lima.abc` is needed to avoid circular imports of fields needing to
     know about schemas and vice versa. The base classes are used for internal
     type checks. For users of the library there should be no need to use
     :mod:`lima.abc` directly.
  
  '''
  
  
  class FieldABC:
      '''Abstract base class for fields.
  
      Inheriting from :class:`FieldABC` marks a class as a field for internal
      type checks.
  
      (Usually, it's a *way* better Idea to subclass :class:`lima.fields.Field`
      directly)
  
      '''
      pass
  
  
  class SchemaABC:
      '''Abstract base class for schemas.
  
      Inheriting from :class:`SchemaABC` marks a class as a schema for internal
      type checks.
  
      (Usually, it's a *way* better Idea to subclass :class:`lima.schema.Schema`
      directly)
  
      Note that every Schema class must provide a mapping :attr:`__fields__` as a
      class attribute. Typically, this is taken care of by
      :class:`lima.schema.SchemaMeta` when subclassing
      :class:`lima.schema.Schema`.
  
      '''
      pass
  
subject: Improve docstring for SchemaABC