text: 'use strict'
  
  var isStream = (module.exports = function(stream) {
      return stream !== null && typeof stream === 'object' && typeof stream.pipe === 'function'
  })
  
  isStream.writable = function(stream) {
      return (
          isStream(stream) &&
          stream.writable !== false &&
          typeof stream._write === 'function' &&
          typeof stream._writableState === 'object'
      )
  }
  
  isStream.readable = function(stream) {
      return (
          isStream(stream) &&
          stream.readable !== false &&
          typeof stream._read === 'function' &&
          typeof stream._readableState === 'object'
      )
  }
  
  isStream.duplex = function(stream) {
      return isStream.writable(stream) && isStream.readable(stream)
  }
  
  isStream.transform = function(stream) {
      return (
          isStream.duplex(stream) && typeof stream._transform === 'function' && typeof stream._transformState === 'object'
      )
  }
  