For deme U, the population count was 4195 until a change 9423.84 generations ago, where it changed to 8813, remaining steady thereafter.
time_units: generations
demes:
  - name: U
    start_time: .inf
    epochs:
      - start_size: 4195
        end_time: 9423.84
      - start_size: 8813
        end_time: 0