For deme D, the population count was 6034 until a change 6638.749 generations ago, where it changed to 4226, remaining steady thereafter.
time_units: generations
demes:
  - name: D
    start_time: .inf
    epochs:
      - start_size: 6034
        end_time: 6638.749
      - start_size: 4226
        end_time: 0