text: import tempfile
  import urllib.request
  
  from pdbfixer.pdbfixer import proteinResidues, rnaResidues, dnaResidues
  
  def tmp_pdb_filename():
  
      filename=tempfile.NamedTemporaryFile(suffix=".pdb").name
      return filename
  
  
  def download_pdb(pdb_id=None, output_filepath=None):
  
      filetype='pdb'
      fullurl = 'https://files.rcsb.org/download/'+pdb_id.capitalize()+'.'+filetype
  
      if output_file is None:
          filename=tmp_pdb_filename()
          urllib.request.urlretrieve(fullurl, filename)
          return filename
      else:
          urllib.request.urlretrieve(fullurl, output_filepath)
          pass
  
  