code: def test_get_df():
      ppdb = PandasMmcif()
      ppdb.read_mmcif(TESTDATA_FILENAME)
  
      shape = ppdb.get("c-alpha").shape
      assert shape == (174, 21), shape
  
      shape = ppdb.get("hydrogen", invert=True, records=("ATOM",)).shape
      assert shape == (1330, 21), shape
  
      # deprecated use of string
      shape = ppdb.get("hydrogen", invert=True, records="ATOM").shape
      assert shape == (1330, 21), shape
  
      shape = ppdb.get("hydrogen").shape
      assert shape == (0, 21), shape
  
      shape = ppdb.get("main chain", records=("ATOM",)).shape
      assert shape == (696, 21), shape
  
      shape = ppdb.get("heavy", records=("ATOM",)).shape
      assert shape == (1330, 21), shape
  
      shape = ppdb.get("carbon", records=("ATOM",)).shape
      assert shape == (857, 21), shape
  
imports: import os
  from urllib.error import HTTPError
  from urllib.request import urlopen
  from pathlib import Path
  import numpy
  import pandas
  from biopandas.mmcif import PandasMmcif
  from biopandas.pdb import PandasPdb
  from biopandas.testutils import assert_raises
  from nose.tools import raises
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 12 for calling a global function with example usage: test_get_df() without return types