'return a suitable array argument for testing the letter type'

def _arg_for_type(self, a_letter_type, index=0):

    if (a_letter_type in 'bhilq'):
        return np.array([1, 4, 0, (-2)], dtype=a_letter_type)
    if (a_letter_type in 'BHILQ'):
        return np.array([1, 2, 4, 0], dtype=a_letter_type)
    elif (a_letter_type in '?'):
        return np.array([True, False, False, True], dtype=a_letter_type)
    elif (a_letter_type[0] == 'm'):
        if (len(a_letter_type) == 1):
            a_letter_type = 'm8[D]'
        return np.array([2, (-3), 'NaT', 0], dtype=a_letter_type)
    elif (a_letter_type[0] == 'M'):
        if (len(a_letter_type) == 1):
            a_letter_type = 'M8[D]'
        return np.array(['Nat', 1, 25, 0], dtype=a_letter_type)
    elif (a_letter_type in 'fd'):
        return np.array([1.5, (-3.5), 0.0, float('nan')], dtype=a_letter_type)
    elif (a_letter_type in 'FD'):
        if (sys.platform != 'win32'):
            negzero = (- (0.0 + 1j))
        else:
            negzero = (0.0 - 1j)
        return np.array([negzero, (1.5 + 1.5j), (1j * float('nan')), 0j], dtype=a_letter_type)
    else:
        raise RuntimeError(('type    %r    not    understood' % (a_letter_type,)))
