old_contents: from typing import NamedTuple
  from datetime import datetime
  
  
  class Demand(NamedTuple):
      event: Event
      audience: int
  
  
  class Event(NamedTuple):
      name: str
      type: EventType
  
  
  class EventType(NamedTuple):
      name: str
  
  
  class Person(NamedTuple):
      name: str
  
  
  class Role(NamedTuple):
      name: str
  
  
  class Room(NamedTuple):
      name: str
      capacity: int
  
  
  class Session(NamedTuple)
      slots: Sequence[Slot]
  
  
  class Slot(NamedTuple):
      starts_at: datetime
      ends_at: datetime
  
  
  class Unavailability(NamedTuple):
      person: Person
      slot: Slot
  
new_contents: from typing import NamedTuple
  from datetime import datetime
  
  
  class Demand(NamedTuple):
      event: Event
      audience: int
  
  
  class Event(NamedTuple):
      name: str
      type: EventType
  
  
  class EventType(NamedTuple):
      name: str
  
  
  class Person(NamedTuple):
      name: str
  
  
  class Role(NamedTuple):
      name: str
  
  
  class Room(NamedTuple):
      name: str
      capacity: int
  
  
  class Session(NamedTuple):
      slots: Sequence[Slot]
  
  
  class Slot(NamedTuple):
      starts_at: datetime
      ends_at: datetime
  
  
  class Unavailability(NamedTuple):
      person: Person
      slot: Slot
  
subject: Fix typo