code: @Nullable
    public static Schema getSchemaOfImplementationClass (@Nullable final Class <?> aImplClass)
    {
      final EUBLTRDocumentType eDocType = getDocumentTypeOfImplementationClass (aImplClass);
      return eDocType == null ? null : eDocType.getSchema ();
    }
docs: Get the XSD Schema object for the UBLTR document type of the passed
  implementation class.
  
  @param aImplClass
  The implementation class of any UBLTR document type. May be
  <code>null</code>.
  @return <code>null</code> if no such UBLTR document type exists.