code: def header(self, definitions, parent, root):
          
          if root is None:
              return
          header = Facade('Header')
          parent.headers.append(header)
          header.use = root.get('use', default='literal')
          ns = root.get('namespace')
          if ns is None:
              header.namespace = definitions.tns
          else:
              prefix = root.findPrefix(ns, 'h0')
              header.namespace = (prefix, ns)
          msg = root.get('message')
          if msg is not None:
              header.message = msg
          part = root.get('part')
          if part is not None:
              header.part = part
docs: add the input/output header properties