whole_func_string: function incidenceId(u, v) {
    return u < v ?  u.length + ':' + u + '-' + v : v.length + ':' + v + '-' + u;
  }
func_code_string: function incidenceId(u, v) {
    return u < v ?  u.length + ':' + u + '-' + v : v.length + ':' + v + '-' + u;
  }
func_documentation_string: /*
  This id can be used to group (in an undirected manner) multi-edges
  incident on the same two nodes.