# File lib/rgen/fragment/model_fragment.rb, line 226
  def unresolve_external_fragment(fragment)
    return if @resolved_refs.nil?
    raise "can not unresolve, missing fragment information" if @resolved_refs == :dirty || @resolved_refs[:unknown]
    rrefs = @resolved_refs[fragment]
    @resolved_refs.delete(fragment)
    unresolve_refs(rrefs) if rrefs
  end