code: def is_design_matrix(obj):
      from patsy import DesignMatrix
  
      return isinstance(obj, DesignMatrix)
  
file_path: statsmodels/statsmodels/tools/data.py
imports: from statsmodels.compat.numpy import NP_LT_2
  import numpy
  import pandas
label_desc: Use image node_id 3 for calling a global function with example usage: is_design_matrix(obj) and returns: isinstance