code: def test_fetch_pdb():
      """Test fetch_pdb"""
  
      try:
          ppdb = PandasPdb()
          url, txt = ppdb._fetch_pdb("3eiy")
      except HTTPError:
          url, txt = None, None
      except ConnectionResetError:
          url, txt = None, None
  
      if txt:  # skip if PDB down
          txt[:100] == three_eiy[:100]
          ppdb.fetch_pdb("3eiy")
          assert ppdb.pdb_text == txt
          assert (
              ppdb.pdb_path
              == "https://files.rcsb.org/download/3eiy.pdb"
          )
  
file_path: biopandas/biopandas/pdb/tests/test_read_pdb.py
imports: import os
  from urllib.error import HTTPError, URLError
  from urllib.request import urlopen
  import numpy
  import pandas
  from biopandas.pdb import PandasPdb
  from biopandas.testutils import assert_raises
  from nose.tools import raises
label_desc: Use image node_id 3 for calling a global function with example usage: test_fetch_pdb() without return types