public Set<AbsoluteUnixPath> getVolumes() {
    return new HashSet<>(volumes);
  }
Creates and returns a default platform if the user hasn't added or set any platforms ,else
returns a list of user specified platforms .

@return platforms a list of user specified platforms.
jib-build-plan/src/main/java/com/google/cloud/tools/jib/api/buildplan/ContainerBuildPlan.java