Implementing softmax function. Only softsign and softplus are available

Hi all! I tried adding the softmax function and it's tf function to the Interval bound propagation's (ibp's) code in the dictionary it refers to. But then I see an error as: 'NotImplementedError: tf.nn.softmax modules are not supported by "RelativeIntervalBounds" '. Is there a work-around for this or some changes that I can make to the sonnet or ibp source files? Please help me out. I'm trying to verify a VGG16 architecture. I was earlier trying to verify a GoogLenet but I was not sure how to implement the inception layers.
Thanks in advance.