bagIterIsSuperbag = xyi => {
  for (const [_m, xc, yc] of xyi) {
    if (xc < yc) {
      // something in y is not in x, so x is not a superbag of y
      return false;
    }
  }
  return true;
}
@template T
@param {Iterable<[T,bigint,bigint]>} xyi
@returns {boolean}