code: def is_constant(s, dropna=True) -> bool:
      if dropna:
          s = s[pd.notna(s)]
      a = s.to_numpy()
      return True if a.size == 0 else bool((a[0] == a).all())
  
file_path: upgini/src/upgini/utils/cv_utils.py
imports: from typing import Any, Dict, Optional, Union
  import pandas
  from sklearn.model_selection import BaseCrossValidator, KFold, TimeSeriesSplit, GroupKFold, GroupShuffleSplit
  from upgini.metadata import CVType
  from upgini.utils.blocked_time_series import BlockedTimeSeriesSplit
label_desc: Use image node_id 1 for calling a global function with example usage: is_constant(s, dropna) and returns: unknown