code: def test_find_all_variables(df_vartypes):
      all_vars = ["Name", "City", "Age", "Marks", "dob"]
      all_vars_no_dt = ["Name", "City", "Age", "Marks"]
      user_vars = ["Name", "City"]
      non_existing_vars = ["Grades"]
  
      assert _find_all_variables(df_vartypes) == all_vars
      assert (
          _find_all_variables(df_vartypes, exclude_datetime=True)
          == all_vars_no_dt
      )
      assert (
          _find_all_variables(df_vartypes, ["Name", "City"])
          == user_vars
      )
  
      with pytest.raises(KeyError):
          assert _find_all_variables(df_vartypes, non_existing_vars)
  
file_path: feature_engine/tests/test_variable_handling/test_variable_type_selection.py
imports: import pandas
  import pytest
  from feature_engine._variable_handling.variable_type_selection import _filter_out_variables_not_in_dataframe, _find_all_variables, _find_categorical_and_numerical_variables, _find_or_check_categorical_variables, _find_or_check_datetime_variables, _find_or_check_numerical_variables
label_desc: Use image node_id 7 for calling a global function with example usage: test_find_all_variables(df_vartypes) without return types