Added getters for dynslice (#3019)

* Added getters for dynslice

* Style check fixes

src/ngraph/op/experimental/dyn_slice.hpp

@@ -49,6 +49,11 @@ namespace ngraph
                      const AxisSet& shrink_axis = AxisSet{},
                      const AxisSet& ellipsis_mask = AxisSet{});
 
+            const AxisSet& get_lower_bounds_mask() const { return m_lower_bounds_mask; }
+            const AxisSet& get_upper_bounds_mask() const { return m_upper_bounds_mask; }
+            const AxisSet& get_new_axis() const { return m_new_axis; }
+            const AxisSet& get_shrink_axis() const { return m_shrink_axis; }
+            const AxisSet& get_ellipsis_mask() const { return m_ellipsis_mask; }
             virtual std::shared_ptr<Node>
                 copy_with_new_args(const NodeVector& new_args) const override;