from typing import Optional


def _is_in_range(a_list: list,
                 min: Optional[float] = None,
                 max: Optional[float] = None) -> bool:
    """
    Return True if `a_list` ontains values between `min` and `max`, False
    otherwise
    """
    for el in a_list:
        if min is not None:
            if el < min:
                return False
        if max is not None:
            if el > max:
                return False
    return True