Swagger Error: Not a valid parameter definition for Multi part file type

[27081988]

I'm trying to generate swagger document for my API's .
Every time I get "Swagger Error: Not a valid parameter definition." when paste json into swagger editor.
When I checked generated json it contains "ref" instead of "file".
I tried following options but none of them works.
@ApiImlicitParams(value={ @ApiImlicitParam=(paramType=form, name=file, value="file", required=true, dataType="file"})
or
@ApiImlicitParams(value={ @ApiImlicitParam=(paramType=formData, name=file, value="file", required=true, dataType="file"})
or
@ApiImlicitParams(value={ @ApiImlicitParam=(paramType=form, name=file, value="file", required=true, dataType="_file"})
or
@ApiImlicitParams(value={ @ApiImlicitParam=(paramType=form, name=file, value="file", required=true, dataType="java.io.InputStream"})
or
@ApiImlicitParams(value={ @ApiImlicitParam=(paramType=form, name=file, value="file", required=true, dataType="MultipartFile"})

method(@RequestPart(value= "file", required=true) MultipartFile file)