code: function getObservedBits(name, item) {
      if (NAME_BITS.hasOwnProperty(name)) {
        return NAME_BITS[name]
      } else {
        const bits = 1 << NAME_COUNT++
        return (NAME_BITS[name] = bits)
      }
    }
docs: get the observed bits (bitmask) for a given top-level name note: every 32nd name will share a bitmask