def METHOD_NAME(self, alpha=0):
    """estimates the regularized inverse covariance using nodewise
    regression
    Parameters
    ----------
    alpha : scalar
        Regularizing constant
    """
    n, p = self.exog.shape
    nodewise_row_l = []
    nodewise_weight_l = []
    for idx in range(p):
        nodewise_row = _calc_nodewise_row(self.exog, idx, alpha)
        nodewise_row_l.append(nodewise_row)
        nodewise_weight = _calc_nodewise_weight(self.exog, nodewise_row,
                                                idx, alpha)
        nodewise_weight_l.append(nodewise_weight)
    nodewise_row_l = np.array(nodewise_row_l)
    nodewise_weight_l = np.array(nodewise_weight_l)
    approx_inv_cov = _calc_approx_inv_cov(nodewise_row_l,
                                          nodewise_weight_l)
    self._approx_inv_cov = approx_inv_cov