def split_ring(grid):
    """ Reinforce MV grid by splitting a critical ring into two new rings according to dena
    
    Parameters
    ----------
        grid : :class:`~.ding0.core.network.grids.MVGridDing0`
            Grid identifier.
          
    Returns
    -------
    type 
        #TODO: Description of return. Change type in the previous line accordingly
    """
    pass
