For deme Z, the population count was 903 until a change 3359.8 generations ago, where it changed to 5292, remaining steady thereafter.
time_units: generations
demes:
  - name: Z
    start_time: .inf
    epochs:
      - start_size: 903
        end_time: 3359.8
      - start_size: 5292
        end_time: 0