code: function getUpperBoundMatcher(compare, query) {
  		// No lower bound
  		if (!query.hasOwnProperty('$lt') && !query.hasOwnProperty('$lte')) {
  			return function () { return true; };
  		}
  		if (query.hasOwnProperty('$lt') && query.hasOwnProperty('$lte')) {
  			if (compare(query.$lte, query.$lt) === 0) {
  				return function (key) { return compare(key, query.$lt) < 0; };
  			}
  			if (compare(query.$lte, query.$lt) < 0) {
  				return function (key) { return compare(key, query.$lte) <= 0; };
  			} else {
  				return function (key) { return compare(key, query.$lt) < 0; };
  			}
  		}
  		if (query.hasOwnProperty('$lt')) {
  			return function (key) { return compare(key, query.$lt) < 0; };
  		} else {
  			return function (key) { return compare(key, query.$lte) <= 0; };
  		}
  	}
docs: Return a function that tells whether a given key matches an upper bound