Grouping in wrap-sequence

As currently specified, I don't understand what wrap-sequence does.
Given:

  <p:wrap-sequence>
    <p:input port="source">
      <p:inline><doc label="a"/></p:inline>
      <p:inline><doc label="a"/></p:inline>
      <p:inline><doc label="b"/></p:inline>
      <p:inline><doc label="a"/></p:inline>
    </p:input>
    <p:option name="wrapper" value="wrapme"/>
  </p:wrap-sequence>

I think the output is:

<wrapme>
<doc label="a"/>
<doc label="a"/>
<doc label="b"/>
<doc label="a"/>
</wrapme>

What is the output of

  <p:wrap-sequence>
    <p:input port="source">
      <p:inline><doc label="a"/></p:inline>
      <p:inline><doc label="a"/></p:inline>
      <p:inline><doc label="b"/></p:inline>
      <p:inline><doc label="a"/></p:inline>
    </p:input>
    <p:option name="wrapper" value="wrapme"/>
    <p:option name="group-adjacent" value="@label='a'"/>
  </p:wrap-sequence>

Don't we need another wrapper element?

                                        Be seeing you,
                                          norm

-- 
Norman Walsh <ndw@nwalsh.com> | The firmest line that can be drawn upon
http://nwalsh.com/            | the smoothest paper is still jagged
                              | edges if seen through a microscope.
                              | This does not matter until important
                              | deductions are made on the supposition
                              | that there are no jagged edges.--Samuel
                              | Butler (II)