def dot(v1, v2):
    """
    Function calculates the dot product

    Parameters
    ----------------
    v1: numpy.array
        Input array
    v2: numpy.array
        Input array

    Returns
    ------------
    The dot product of the two arrays
    """
    xx = v1[0, :]*v2[0, :]
    yy = v1[1, :]*v2[1, :]
    zz = v1[2, :]*v2[2, :]

    return xx + yy + zz