code: func mergeSpec(dest, source *spec.Swagger) {
  	if source == nil || source.Paths == nil {
  		return
  	}
  	if dest.Paths == nil {
  		dest.Paths = &spec.Paths{}
  	}
  	for k, v := range source.Definitions {
  		if dest.Definitions == nil {
  			dest.Definitions = spec.Definitions{}
  		}
  		dest.Definitions[k] = v
  	}
  	for k, v := range source.Paths.Paths {
  		if dest.Paths.Paths == nil {
  			dest.Paths.Paths = map[string]spec.PathItem{}
  		}
  		dest.Paths.Paths[k] = v
  	}
  }
docs: // mergeSpec copies paths and definitions from source to dest, mutating dest, but not source.
  // We assume that conflicts do not matter.