code: def test_pandas_api(self):
      df = pd.DataFrame({"f1": [1, 2], "f2": [3, 4]})
      array, _ = convert_to_jtensor(df, feature_columns=["f1"])
      self.assert_(isinstance(array, JTensor))
      self.assertEqual(array.storage.shape, (2, 1))
  
imports: import unittest
  import pandas
  from bigdl.ppml.fl.data_utils import *
label_desc: Use image node_id 1 for calling the TestDataUtils obj's underlying member method code with example usage: obj.test_pandas_api() without return types