import math


def get_normalized(vector):
    """Returns normalized vector (2-norm) or None, if vector is (0, 0).

    :param vector: of this vector a normalized version will be calculated
    :type vector: 2d list
    :rtype: normalized version of the vector
    """

    result = None
    x = vector[0]
    y = vector[1]
    if not (x == 0 and y == 0):
        #Norm of (0,0) is not defined.
        n = math.sqrt(x*x+y*y)
        result = [x/n, y/n]
    return result