code: def _serialize(
              self,
              array_parent,  # type: ET.Element
              value,  # type: List
              state  # type: _ProcessorState
      ):
          # type: (...) -> None
          
          if not value:
              # Nothing to do. Avoid attempting to iterate over a possibly
              # None value.
              return
  
          for i, item_value in enumerate(value):
              state.push_location(self._item_processor.element_path, i)
              item_element = self._item_processor.serialize(item_value, state)
              array_parent.append(item_element)
              state.pop_location()
docs: Serialize the array value and add it to the array parent element.