[Feature request] Ability to ignore some code portions

It would sometimes be desirable to omit a certain line of code or certain function from the heatmap, I'm thinking something along the lines of [pylint's disable comments](https://github.com/tensorflow/tensorflow/blob/a61a816f86bb35d1d3a58f1c9a236be5e14c55c7/tensorflow/python/keras/layers/core.py#L65)