code: func NewMustRunAs(ranges []policy.IDRange) (GroupStrategy, error) {
  	if len(ranges) == 0 {
  		return nil, fmt.Errorf("ranges must be supplied for MustRunAs")
  	}
  	return &mustRunAs{
  		ranges: ranges,
  	}, nil
  }
docs: // NewMustRunAs provides a new MustRunAs strategy based on ranges.