output required :-

<Document xmlns="urn:iso:std:iso:20022:tech:xsd:pain.001.001.03" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">



code written by me :-
document = lo_document->create_simple_element(
                                     name    = 'Document'
                                     parent  = lo_document ).


lv_document =  document->set_attribute( name = 'xmlns'
                                        value =  lv_namespace ).