code: function checkMediaType(key, value)
  {
    if(typeof value != 'string')
      throw SyntaxError(key+' param should be a String, not '+typeof value);
  
    if(!value.match('AUDIO|DATA|VIDEO'))
      throw SyntaxError(key+' param is not one of [AUDIO|DATA|VIDEO] ('+value+')');
  }
docs: Type of media stream to be exchanged.
  Can take the values AUDIO, DATA or VIDEO.
  
  @typedef core/complexTypes.MediaType
  
  @type {(AUDIO|DATA|VIDEO)}
   
  Checker for {@link module:core/complexTypes.MediaType}
  
  @memberof module:core/complexTypes
  
  @param {external:String} key
  @param {module:core/complexTypes.MediaType} value