code: def get_column(self, i: int) -> np.ndarray:
      if self._X_cache is None:
          self._X_cache = self.values[~self.mask, :]
      return self._X_cache[:, i]
  
imports: from operator import gt, le
  from typing import Any, List, Optional, Union
  import numpy
  import pandas
  from .errors import NoSplittableVariableException
  from .splitcondition import SplitCondition
label_desc: Use image node_id 4 for calling the CovariateMatrix obj's underlying member method code with example usage: obj.get_column(i) and returns: self