def get_invalid_keys(validation_warnings):
    """Get the invalid keys from a validation warnings list.

    Args:
        validation_warnings (list): A list of two-tuples where the first
            item is an iterable of string args keys affected and the second
            item is a string error message.

    Returns:
        A set of the string args keys found across all of the first elements in
        the validation tuples.

    """
    invalid_keys = set([])
    for affected_keys, error_msg in validation_warnings:
        for key in affected_keys:
            invalid_keys.add(key)
    return invalid_keys