def create_matrix33_view(mat):
    """Returns a view into the matrix in Matrix33 format.

    This is different from matrix33.create_from_matrix44, in that
    changes to the returned matrix will also alter the original matrix.

    :rtype: numpy.array
    :return: A view into the matrix in the format of a matrix33 (shape (3,3)).
    """
    return mat[0:3, 0:3]
