For deme B, the population count was 696 until a change 1909.06 generations ago, where it changed to 9126, remaining steady thereafter.
time_units: generations
demes:
  - name: B
    start_time: .inf
    epochs:
      - start_size: 696
        end_time: 1909.06
      - start_size: 9126
        end_time: 0