def get_subgroup(grp, subgr_name) :
    """For hdf5:
       returns subgroup of the group if it exists or creates and returns new subgroup
    """    
    #print 'YYY grp.name:', grp.name, '  subgr_name:', subgr_name
    if subgr_name in grp : return grp[subgr_name]
    return grp.create_group(subgr_name)