text: 'use strict'
  
  var isNumeric = require('isnumeric')
  var argsToArray = require('args-to-array')
  
  module.exports = function sum (numbers) {
    numbers = Array.isArray(numbers) ? numbers : argsToArray(arguments)
    return numbers.reduce(function (previous, next) {
      if (!isNumeric(previous) || !isNumeric(next)) {
        throw new Error('All values must be numbers')
      } else {
        return (+previous) + (+next)
      }
    })
  }
  