sample_shifts_edges attempts to find K shifts in the tree which allocations
are parsimonious. The actual generation of edges is done by function
sample_edges_intervals.
sample_shifts_edges(tree, K, part.list = enumerate_tips_under_edges(tree))vector of edges
: input tree
: number of edges to be sampled.
This function uses function enumerate_tips_under_edges to generate a list
of tips under each edge, and function check_parsimony to check for
parsimony of a given solution, under the assumption of an "infinite site model".