code: def _to_dense_discrete_array(f: np.ndarray) -> np.ndarray:
      ret = f.astype(bytes)
      ret[pd.isnull(f)] = _NONE_STR
      return ret
  
imports: import functools
  import itertools
  import math
  from typing import Any, List, Optional, Tuple, Union
  import uuid
  import numpy
  import pandas
  import scipy.special
  import sklearn.neighbors
label_desc: Use image node_id 5 for calling a global function with example usage: _to_dense_discrete_array(f) and returns: ret