def __init__(self, child: Node, top: float = 0.05, bottom: Optional[float] = None, **resource_args):
      if bottom is None:
          bottom = top
      lo = top
      hi = 1.0 - bottom
      super().__init__(child, f=MarkDropHeaderFooter.mark_drop_header_and_footer, args=[lo, hi], **resource_args)
  
  @staticmethod
  @timetrace("markHeadFoot")
  def mark_drop_header_and_footer(parent: Document, lo: float, hi: float) -> Document:
      for elem in parent.elements:
          bbox = elem.data.get("bbox")
          if (bbox is not None) and ((bbox[1] > hi) or (bbox[3] < lo)):
              elem.data["_drop"] = True  # mark for removal
      return parent