code: def std_func(x):
      """standard deviation function for example"""
      return 0.1 * np.exp(2.5 + 0.75 * np.abs(x))
  
file_path: statsmodels/statsmodels/robust/tests/test_mquantiles.py
imports: import numpy
  from numpy.testing import assert_allclose
  import pandas
  from statsmodels.regression.linear_model import OLS
  from statsmodels.regression.quantile_regression import QuantReg
  from statsmodels.robust import norms
  from statsmodels.robust.robust_linear_model import RLM
label_desc: Use image node_id 2 for calling a global function with example usage: std_func(x) and returns: unknown