code: function unitFactory (name, valueStr, unitStr) {
    const dependencies = ['config', 'Unit', 'BigNumber']
  
    return factory(name, dependencies, ({ config, Unit, BigNumber }) => {
      // Note that we can parse into number or BigNumber.
      // We do not parse into Fractions as that doesn't make sense: we would lose precision of the values
      // Therefore we dont use Unit.parse()
      const value = config.number === 'BigNumber'
        ? new BigNumber(valueStr)
        : parseFloat(valueStr)
  
      const unit = new Unit(value, unitStr)
      unit.fixPrefix = true
      return unit
    })
  }
docs: helper function to create a factory function which creates a physical constant, a Unit with either a number value or a BigNumber value depending on the configuration