time_units: generations
defaults:
  migration:
    demes: [a, b, c]
demes:
- name: a
  epochs:
  - {start_size: 1}
- name: b
  epochs:
  - {start_size: 1}
- name: c
  epochs:
  - {start_size: 1}
- name: x
  epochs:
  - {start_size: 1}
- name: y
  epochs:
  - {start_size: 1}
migrations:
- {rate: 0.1, start_time: 200, end_time: 100}
- rate: 0.2
  demes: [a, b]
  start_time: 100
  end_time: 0
- {rate: 0.3, demes: null, source: x, dest: y}