from typing import List


def validate_straight(values: List[int]) -> bool:
    """Helper to check for a straight
    (any length sequence, in order, no missing middle values).

    Parameters
    ----------
    values : list of int
        Values to check.

    Returns
    -------
    is_straight : bool
        Whether `values` form a straight.
        All values must be in the straight, with no duplicates.
    """
    # check that the minimum and maximum ranks are spaced properly
    ranks_check = max(values) - min(values) + 1 == len(values)
    # check that all values are unique
    unique_check = len(set(values)) == len(values)
    return ranks_check and unique_check