from typing import Optional


def get_vote(message: str) -> Optional[str]:
    """Check if the message is composed only by -'s or + 's.

    Args:
        message: message received from the user

    Returns:
        The return value + if the message is only +, - if the message is only -, and None otherwise
    """
    if all(x == '-' for x in message):
        return '-'

    if all(c == '+' for c in message):
        return '+'

    return None