code: def test_sortino_ratio():
      assert sortino_ratio(0.5, 0.0, 0.02) is np.NaN
      assert sortino_ratio(0.005, 8.5, 0.005) == 0.0
  
file_path: FinQuant/tests/test_quants.py
imports: import pdb
  import numpy
  import pandas
  import pytest
  from finquant.quants import annualised_portfolio_quantities, downside_risk, sharpe_ratio, sortino_ratio, treynor_ratio, value_at_risk, weighted_mean, weighted_std
label_desc: Use image node_id 4 for calling a global function with example usage: test_sortino_ratio() without return types