docs: def is_ergodic(T, tol):
      """
      checks if T is 'ergodic'
  
      Parameters
      ----------
      T : scipy.sparse matrix
          Transition matrix
      tol : float
          tolerance
  
      Returns
      -------
      Truth value : bool
      True, if # strongly connected components = 1
      False, otherwise
      """
      if isdense(T):
          T = T.tocsr()
      if not is_transition_matrix(T, tol):
          raise ValueError("given matrix is not a valid transition matrix.")
  
      num_components = connected_components(T, directed=True, \
                                            connection='strong', \
                                            return_labels=False)
  
      return num_components == 1