A transition metal \( (M) \) among \( \mathrm{Mn} \), \( \mathrm{Cr} \), \( \mathrm{Co} \) and \( \mathrm{Fe} \) has the highest standard electrode potential \( (M^{3+} / M^{2+}) \). It forms a metal complex of the type \( [M(CN)_6]^{4-} \). The number of electrons present in the \( e_g \) orbital of the complex is ____________.