time_units: generations
demes:
- name: deme1
  epochs:
  - {start_size: 1000, end_time: 0}
- name: deme2
  epochs:
  - {end_time: 100, start_size: 1000}
pulses:
- {sources: [deme1], dest: deme2, proportions: [0.1], time: string}