[R]: remove override of is.matrix for FM.
[R]: remove override of is.matrix for FM.

flashxio/FlashX,icoming/FlashGraph,flashxio/FlashX,icoming/FlashGraph,icoming/FlashX,flashxio/FlashX,icoming/FlashX,flashxio/FlashX,icoming/FlashGraph,icoming/FlashGraph,flashxio/FlashX,icoming/FlashX,icoming/FlashGraph,icoming/FlashX,icoming/FlashX,flashxio/FlashX