code: function guessType (key) {
      var type = 'boolean'
  
      if (checkAllAliases(key, flags.strings)) type = 'string'
      else if (checkAllAliases(key, flags.numbers)) type = 'number'
      else if (checkAllAliases(key, flags.arrays)) type = 'array'
  
      return type
    }
docs: given a flag, enforce a default type.