code: def df_constant_features():
      data = {
          "Name": ["tom", "nick", "krish", "jack"],
          "City": ["London", "Manchester", "Liverpool", "Bristol"],
          "Age": [20, 21, 19, 18],
          "Marks": [0.9, 0.8, 0.7, 0.6],
          "dob": pd.date_range("2020-02-24", periods=4, freq="T"),
          "const_feat_num": [1, 1, 1, 1],
          "const_feat_cat": ["a", "a", "a", "a"],
          "quasi_feat_num": [1, 1, 1, 2],
          "quasi_feat_cat": ["a", "a", "a", "b"],
      }
  
      df = pd.DataFrame(data)
  
      return df
  
file_path: feature_engine/tests/test_selection/test_drop_constant_features.py
imports: import numpy
  import pandas
  import pytest
  from feature_engine.selection import DropConstantFeatures
label_desc: Use image node_id 1 for calling a global function with example usage: df_constant_features() and returns: df