Fix crash caused by parallel formatting of classes.

      @relations = nil

    end

    # Accessors for internal doc object.  These are used to run

    # ClassFormatter on the internal doc object and then assign it

    # back.

    # Returns the internal doc object.

    def internal_doc

      @doc

    end

    # Sets the internal doc object.

    #

    # The doc object is processed in parallel and then assigned back

    # through this method.  But because of parallel processing the

    # assigned doc object will not be just a modified old @doc but a

    # completely new.  If we were to just assign to @doc the

    # #find_members caches would still point to old @doc members

    # resulting in mysterious errors further along...

    def internal_doc=(doc)

      @doc = doc

      @doc.merge!(doc) do |key, oldval, newval|

        if key == :members

          oldval.zip(newval) do |ms|

            ms[0].merge!(ms[1])

          end

          oldval

        else

          newval

        end

      end

    end

    # Accessor to internal hash