title: Type of object received during file upload using @UploadFile
body: <p>In the REST API below, what is the type of file object that is received. </p>
  
  <pre><code>@Post('/:folderId/documents/:fileName')
  @UseInterceptors(FileInterceptor('file'))
  @ApiConsumes('multipart/form-data')
  @ApiImplicitParam({ name: 'folderId', description: ' Folder Id' })
  @ApiImplicitParam({ name: 'fileName', description: ' File Name' })
  @ApiImplicitFile({ name: 'file', required: true, description: 'PDF File' })
  async uploadFile(@UploadedFile() file, @Param() folderId, @Param() fileName) {
  /**
   * I need to know the type of file object (first argument) of uploadFile
   */
      this.folderService.uploadFile(file, folderId, fileName);
  }
  </code></pre>
  
  <p>I need to write a file received in the request to disk. How to do that?</p>