def _check_required_parameters(dictionary_of_params, required_params):
    """
    Check that all required parameters are inputted
    :param dictionary_of_params: is a dictionary of parameters from playbook
    :param required_params: is a set of required parameters
    :return: '' if all required parameters are inputted, else string that contains all missing required parameters
    """
    result = ''
    for element in required_params:
        if not dictionary_of_params.get(element):
            result += '{}, '.format(element)
    result = result[:-2]
    return result
