<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def distanz(x, y=None):
 r""" Calculate the distance between two colon vectors. Parameters x : ndarray First colon vector y : ndarray Second colon vector Returns ------- d : ndarray Distance between x and y Examples -------- array([[0., 1., 2.], [1., 0., 1.], [2., 1., 0.]]) """

    try:
        x.shape[1]
    except IndexError:
        x = x.reshape(1, x.shape[0])

    if y is None:
        y = x

    else:
        try:
            y.shape[1]
        except IndexError:
            y = y.reshape(1, y.shape[0])

    rx, cx = x.shape
    ry, cy = y.shape

    # Size verification
    if rx != ry:
        raise ValueError("The sizes of x and y do not fit")

    xx = (x * x).sum(axis=0)
    yy = (y * y).sum(axis=0)
    xy = np.dot(x.T, y)

    d = abs(np.kron(np.ones((cy, 1)), xx).T +
            np.kron(np.ones((cx, 1)), yy) - 2 * xy)

    return np.sqrt(d)