code: public final boolean isPersistentRepresentationStable()
      {
          boolean is = false;
          Membership membership = _getMembership();
          if (null != membership)
          {
              is = membership.isPersistentRepresentationStable();
          }
          return is;
      }
docs: This method allows an Item to detect if it has a stable representation
  of it's data persisted to disk. If the Items data is in the process of
  being written this method will return false until the writing has completed
  and we have a consistent representation of the Item on disk. e.g. a
  STORE_MAYBE Item will return false for this method until the Item has been
  spilled to disk.
  
  
  NOTE: For STORE_NEVER Items this method doesn't hold much meaning as
  if no representation is ever going to be created it will always be
  stable (even though it doesn't exist).
  
  @return <UL>
  <LI>true - If the persistent representation is stable.</LI>
  <LI>false - If the persistent representation is in the process of being changed.</LI>
  </UL>