Add tf.data.Dataset type check in orca tf keras fit (#2801)
Add tf.data.Dataset type check in orca tf keras fit (#2801)

* add tf.data.Dataset type check in orca tf keras fit

* fix

* remove np

* fix

* remove list

* meet comments

* fix
yangw1234/BigDL,yangw1234/BigDL,yangw1234/BigDL,intel-analytics/BigDL,yangw1234/BigDL,intel-analytics/BigDL,intel-analytics/BigDL,intel-analytics/BigDL