[Feature Request] Support for functional API about kotlindl

[zaleslaw]

So, the early version of Functional API is merged. I close this issue

[zaleslaw]

Hi, @Rishit-dagli agree, this is an important feature.
Currently, it's not supported due to limitation of underlying Java API for TF 1.15 and limitation of C/C++ API:

• Functional API totally based on Concatenate and its children usage (Add, Subtract and another Merge layers)
• Concat operand is available, but gradients are not available for it
• no ability to register custom gradient for analogue of Concat op
• Java TF API for 1.x is frozen

Possible solution:

• Move to Java TF API 2.x (stable version will be released in 2021)
• Update Java TF API with custom gradients for Concat Op (because it has the same issue)
• Write Concatenate-based layers family
• Provide Functional API

As you see, there a lot of work, which should be done in 2021 with TF Java API community