code: def _get_max_sigma(self, R):
          
  
          max_sigma = 2.0 * math.pow(np.nanmax(np.std(R, axis=0)), 2)
          return max_sigma
docs: Calculate maximum sigma of scanner RAS coordinates
  
          Parameters
          ----------
  
          R : 2D array, with shape [n_voxel, n_dim]
              The coordinate matrix of fMRI data from one subject
  
          Returns
          -------
  
          max_sigma : float
              The maximum sigma of scanner coordinates.