docs: def build(self, builder):
          """Build XML by appending to builder"""
  
          params = dict(ItemOID=self.oid, Mandatory=bool_to_yes_no(self.mandatory))
  
          if self.order_number is not None:
              params["OrderNumber"] = str(self.order_number)
  
          if self.key_sequence is not None:
              params["KeySequence"] = str(self.key_sequence)
  
          if self.imputation_method_oid is not None:
              params["ImputationMethodOID"] = self.imputation_method_oid
  
          if self.role is not None:
              params["Role"] = self.role
  
          if self.role_codelist_oid is not None:
              params["RoleCodeListOID"] = self.role_codelist_oid
  
          builder.start("ItemRef", params)
  
          for attribute in self.attributes:
              attribute.build(builder)
          builder.end("ItemRef")