(b)where a rate of interest is stipulated for as due to the mortgagee in respect of the principal amount secured by the mortgage or any portion thereof, in addition to the usufruct from the property, or in respect of any other sum payable to the mortgagee by the mortgagor in his capacity as such Explanation (1) A mortgagee shall be deemed to be in possession of the property mortgaged to him or any portion thereof, notwithstanding that he has leased it to the mortgagor or any other person.