output multipart/form-data  
---
{
  preamble: in0.preamble default '',
  parts: in0.parts ++ {
    'color': {
      headers: {
        'Content-Disposition': {
          name: "color"
        },
        'Content-Type': "text/plain"
      },
      content: "This is the default value for the 'color' parameter"
    }
  }
}