class_docstr: A column composed of numerical data.
  
  This class encodes a standard interface for different types of columns
  containing numerical types of data. In particular, mathematical operations
  that make sense whether a column is integral or real, fixed or floating
  point, should be encoded here.
code: def cov(self, other: NumericalBaseColumn) -> float:
      if (
          len(self) == 0
          or len(other) == 0
          or (len(self) == 1 and len(other) == 1)
      ):
          return cudf.utils.dtypes._get_nan_for_dtype(self.dtype)
  
      result = (self - self.mean()) * (other - other.mean())
      cov_sample = result.sum() / (len(self) - 1)
      return cov_sample
  
imports: from __future__ import annotations
  from typing import Optional, cast
  import numpy
  import cudf
  from cudf import _lib
  from cudf._typing import ScalarLike
  from cudf.core.column import ColumnBase
  from cudf.core.missing import NA
  from cudf.core.mixins import Scannable
label_desc: Use image node_id 10 for calling the NumericalBaseColumn obj's underlying member method code with example usage: obj.cov(other) and returns: cov_sample, cudf