code: def ensure_categorical(arr):
      """
      Ensure that an array-like object is a Categorical (if not already).
  
      Parameters
      ----------
      arr : array-like
          The array that we want to convert into a Categorical.
  
      Returns
      -------
      cat_arr : The original array cast as a Categorical. If it already
                is a Categorical, we return as is.
      """
  
      if not is_categorical(arr):
          from pandas import Categorical
  
          arr = Categorical(arr)
      return arr
  
imports: import warnings
  import numpy
  from pandas._libs import algos, lib
  from pandas._libs.tslibs import conversion
  from pandas.compat import PY3, PY36, string_types
  from pandas.core.dtypes.dtypes import CategoricalDtype, DatetimeTZDtype, ExtensionDtype, IntervalDtype, PandasExtensionDtype, PeriodDtype, registry
  from pandas.core.dtypes.generic import ABCCategorical, ABCDateOffset, ABCDatetimeIndex, ABCIndexClass, ABCPeriodArray, ABCPeriodIndex, ABCSeries
  from pandas.core.dtypes.inference import is_array_like, is_bool, is_complex, is_decimal, is_dict_like, is_file_like, is_float, is_hashable, is_integer, is_interval, is_iterator, is_list_like, is_named_tuple, is_nested_list_like, is_number, is_re, is_re_compilable, is_scalar, is_sequence, is_string_like
label_desc: Use image node_id 2 for calling a global function with example usage: ensure_categorical(arr) and returns: arr