code: @Nonnull
    @ReturnsMutableCopy
    public static MapBasedNamespaceContext createNamespaceMapping (@Nonnull final PSSchema aSchema)
    {
      final MapBasedNamespaceContext ret = new MapBasedNamespaceContext ();
      ret.addDefaultNamespaceURI (CSchematron.NAMESPACE_SCHEMATRON);
      for (final PSNS aItem : aSchema.getAllNSs ())
        ret.addMapping (aItem.getPrefix (), aItem.getUri ());
      return ret;
    }
docs: Helper method to extract the namespace mapping from the provided
  Schematron.
  
  @param aSchema
  The schema to extract the namespace context from. May not be
  <code>null</code>.
  @return A non-<code>null</code> but maybe empty namespace context