<allowed_content_type_list>
 <portal_type id="Purchase Invoice">
  <item>File</item>
  <item>Image</item>
  <item>Invoice Line</item>
  <item>Payment Condition</item>
 </portal_type>
 <portal_type id="Purchase Invoice Module">
  <item>Purchase Invoice</item>
 </portal_type>
 <portal_type id="Sale Invoice">
  <item>File</item>
  <item>Image</item>
  <item>Invoice Line</item>
  <item>Payment Condition</item>
 </portal_type>
 <portal_type id="Sale Invoice Module">
  <item>Sale Invoice</item>
 </portal_type>
</allowed_content_type_list>