code: function getDecoder (encoding) {
    if (!encoding) return null
  
    try {
      return iconv.getDecoder(encoding)
    } catch (e) {
      // error getting decoder
      if (!ICONV_ENCODING_MESSAGE_REGEXP.test(e.message)) throw e
  
      // the encoding was not found
      throw createError(415, 'specified encoding unsupported', {
        encoding: encoding,
        type: 'encoding.unsupported'
      })
    }
  }
docs: Get the decoder for a given encoding.
  
  @param {string} encoding
  @private