code: def n_obsv(self) -> int:
      return self._n_obsv
  
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 15 for calling the CovariateMatrix obj's underlying member method code with example usage: obj.n_obsv() and returns: self