docstr: A covariance matrix is symmetric. For ease of use we make the __getitem__ method symmetric.
docstr_tok: ["A","covariance","matrix","is","symmetric",".","For","ease","of","use","we","make","the","__getitem__","method","symmetric","."]
code: def __getitem__(self, key):
      """
  
      A covariance matrix is symmetric. For ease of use we make the __getitem__ method symmetric.
  
      """
      i, j = key
      try:
          return self.matrix[i, j]
      except KeyError:
          return self.matrix[j, i]
  
imports: from __future__ import annotations
  import abc
  import itertools
  import numpy
  import pandas
  from river import stats, utils
label_desc: Use image node_id 2 for calling the SymmetricMatrix obj's underlying member method code with example usage: obj.__getitem__(key) and returns: self, self