Compute 2SLS standard errors.#'
get_std_err_tsls(yy, xx, lag_nw, k, zz, specs)
A matrix with all endogenous variables.
A matrix with lagged endogenous variables.
Integer. Number of lags for Newey and West
Integer. Value of column to choose from
List. First element contains the estimated standard errors, the second element contains the OLS point estimates.