code: function updateInterpolatedTimes (cfg, callback) {
    const db = cfg.db
    const lastTimepoint = cfg.lastTimepoint
    const nextTimepoint = cfg.nextTimepoint
    const timeDiff = nextTimepoint.arrival_time - lastTimepoint.departure_time
    let literal
    // sqlite null is a string
    if (nextTimepoint.shape_dist_traveled && nextTimepoint.shape_dist_traveled !== 'NULL') {
      // calculate interpolation based off of distance ratios
      const distanceTraveled = nextTimepoint.shape_dist_traveled - lastTimepoint.shape_dist_traveled
      literal = `${lastTimepoint.departure_time} +
        ${timeDiff} *
        (shape_dist_traveled - ${lastTimepoint.shape_dist_traveled}) /
        ${distanceTraveled}`
    } else {
      // calculate interpolation based off of stop sequence ratios
      const numStopsPassed = nextTimepoint.stop_sequence - lastTimepoint.stop_sequence
      literal = `${lastTimepoint.departure_time} +
        ${timeDiff} *
        (stop_sequence - ${lastTimepoint.stop_sequence}) /
        ${numStopsPassed}`
    }
    const updateLiteral = db.sequelize.literal(literal)
    db.stop_time
      .update(
        {
          arrival_time: updateLiteral,
          departure_time: updateLiteral
        },
        {
          where: {
            trip_id: lastTimepoint.trip_id,
            stop_sequence: {
              $gt: lastTimepoint.stop_sequence,
              $lt: nextTimepoint.stop_sequence
            }
          }
        }
      )
      .then(() => {
        callback()
      })
      .catch(callback)
  }
docs: Make an update query to the db to set the interpolated times in
  a particular range of a particular trip