code: def test_empty_pdf():
      pdf_layout = load_pdf("tests/fixtures/io/empty.pdf")
      assert len(pdf_layout) == 1  # Only one page
  
      page_layout = pdf_layout[0]
      assert len(page_layout) == 0
  
imports: import numpy
  from layoutparser.elements import Interval, Rectangle, Quadrilateral, TextBlock, Layout
  from layoutparser import load_json, load_dict, load_csv, load_pdf
label_desc: Use image node_id 4 for calling a global function with example usage: test_empty_pdf() without return types