For deme F, the population count was 6465 until a change 1114.789 generations ago, where it changed to 3303, remaining steady thereafter.
time_units: generations
demes:
  - name: F
    start_time: .inf
    epochs:
      - start_size: 6465
        end_time: 1114.789
      - start_size: 3303
        end_time: 0