2 1  Example: 2 chromosomes with 2 loci each and phase information
1
6    North
n_ind0_a  T
n_ind0_b  c
n_ind1_a  c
n_ind1_b  c
n_ind2_a  A
n_ind2_b  c
4    South
s_ind0_a  G
s_ind0_b  c
s_ind1_a  c
s_ind1_b  c