places a frame around a string
    :Parameters:
        - a_str: string to frame
        - n: number of chars in each line
        - center: center string in frame if True and n > len(str)

    :Example:
        >>> print(chunks_str_frame('the quick brown fox', 44))
        ╔════════════════════════════════════════════╗
        ║            the quick brown fox             ║
        ╚════════════════════════════════════════════╝
        >>> print(chunks_str_frame('the quick brown fox',12, False))
        ╔════════════╗
        ║the quick br║
        ║own fox     ║
        ╚════════════╝

def chunks_str_frame(a_str, n=None, center=True):
    """places a frame around a string
    :Parameters:
        - a_str: string to frame
        - n: number of chars in each line
        - center: center string in frame if True and n > len(str)

    :Example:
        >>> print(chunks_str_frame('the quick brown fox', 44))
        ╔════════════════════════════════════════════╗
        ║            the quick brown fox             ║
        ╚════════════════════════════════════════════╝
        >>> print(chunks_str_frame('the quick brown fox',12, False))
        ╔════════════╗
        ║the quick br║
        ║own fox     ║
        ╚════════════╝
    """
    if n is None:
        n = len(a_str)
    elif n > len(a_str) and center is True:
        a_str = a_str.center(n)
    spcs = "" if n == 1 or n == len(a_str) else " " * (n - (len(a_str) % n))
    n = len(a_str) if n is None else n
    r = chunks_str(a_str, n, "║\n║")
    return "╔{}╗\n║{}{}║\n╚{}╝".format('═' * n, r, spcs, '═' * n)