def validate_hex(hex_string):
    """
    Make sure a string can be hex decoded

    Args:
        hex_string (str): A string of hex characters to check

    Returns:
        boolean: True or False depending on if the string can be hex decoded

    >>> validate_hex('af')
    True
    >>> validate_hex('zh')
    False
    """
    try:
        int(hex_string, 16)
        return True
    except ValueError:
        return False