def rename_dfa_states(dfa: dict, suffix: str):
    """ Side effect on input! Renames all the states of the DFA
    adding a **suffix**.

    It is an utility function to be used to avoid automata to have
    states with names in common.

    Avoid suffix that can lead to special name like "as", "and",...

    :param dict dfa: input DFA.
    :param str suffix: string to be added at beginning of each state name.
    """
    conversion_dict = dict()
    new_states = set()
    new_accepting = set()
    for state in dfa['states']:
        conversion_dict[state] = '' + suffix + state
        new_states.add('' + suffix + state)
        if state in dfa['accepting_states']:
            new_accepting.add('' + suffix + state)
    dfa['states'] = new_states
    dfa['initial_state'] = '' + suffix + dfa['initial_state']
    dfa['accepting_states'] = new_accepting
    new_transitions = dict()
    for transition in dfa['transitions']:
        new_transitions[conversion_dict[transition[0]], transition[1]
            ] = conversion_dict[dfa['transitions'][transition]]
    dfa['transitions'] = new_transitions
    return dfa
