def minimise(ts):
    """
    Returns a tree sequence with the minimal information required to represent
    the tree topologies at its sites.

    This is a convenience function used when we wish to use a subset of the
    sites in a tree sequence for ancestor matching. It is a thin-wrapper
    over the simplify method.
    """
    return ts.simplify(reduce_to_site_topology=True, filter_sites=False)
