def get_A2_hom(s):
    """
    Builds A2 for the spatial error GM estimation with homoscedasticity as in
    Anselin (2011) :cite:`Anselin2011` 

    .. math::

        A_2 = \\dfrac{(W + W')}{2}

    ...

    Parameters
    ----------
    s               : csr_matrix
                      PySAL W object converted into Scipy sparse matrix
    Returns
    -------
    Implicit        : csr_matrix
                      A2 matrix in scipy sparse format
    """
    return (s + s.T) / 2.0
