def check_params(**kwargs):
    """check_params: check whether some parameters are missing
    """
    missing_params = []
    check = True
    for param in kwargs:
        if kwargs[param] is None:
            missing_params.append(param)
    if len(missing_params) > 0:
        print('POT - Warning: following necessary parameters are missing')
        for p in missing_params:
            print('\n', p)
        check = False
    return check
