code: @Nullable
    public String getXMLString (@Nonnull final IPSElement aPSElement)
    {
      ValueEnforcer.notNull (aPSElement, "PSElement");
      final IMicroElement eXML = aPSElement.getAsMicroElement ();
      return MicroWriter.getNodeAsString (getAsDocument (eXML), m_aWriterSettings.getXMLWriterSettings ());
    }
docs: Get the passed Schematron element as a String
  
  @param aPSElement
  The schematron element to convert to a string. May not be
  <code>null</code>.
  @return The passed element as a string or <code>null</code> if
  serialization failed.