docs: def is_transition_matrix(T, tol):
      """
      True if T is a transition matrix
  
      Parameters
      ----------
      T : scipy.sparse matrix
          Matrix to check
      tol : float
          tolerance to check with
  
      Returns
      -------
      Truth value: bool
          True, if T is positive and normed
          False, otherwise
  
      """
      T = T.tocsr()  # compressed sparse row for fast row slicing
      values = T.data  # non-zero entries of T
  
      """Check entry-wise positivity"""
      is_positive = np.allclose(values, np.abs(values), rtol=tol)
  
      """Check row normalization"""
      is_normed = np.allclose(T.sum(axis=1), 1.0, rtol=tol)
  
      return is_positive and is_normed