@CanIgnoreReturnValue
    public Builder setRoots(String first, String... more) {
      List<String> roots = Lists.asList(first, more);
      for (String root : roots) {
        PathType.ParseResult parseResult = pathType.parsePath(root);
        checkArgument(parseResult.isRoot(), "invalid root: %s", root);
      }
      this.roots = ImmutableSet.copyOf(roots);
      return this;
    }
Sets the roots for the file system.

@throws InvalidPathException if any of the given roots is not a valid path for this builder's
    path type
@throws IllegalArgumentException if any of the given roots is a valid path for this builder's
    path type but is not a root path with no name elements
jimfs/src/main/java/com/google/common/jimfs/Configuration.java