An octahedral complex $[\mathrm{Co}(\mathrm{gly}){}_3]$ contains three unsymmetrical bidentate glycinate ligands (N and O donors). The total number of stereoisomers (geometrical plus optical) is

This is $\mathrm{M}(\mathrm{AB}){}_3$. The three N donors can occupy one face (facial) or a meridian (meridional), giving 2 geometrical isomers. Neither has a mirror plane, so each is a pair of enantiomers. Total $=2\times 2=4$.