Not clear how to set custom boundary conditions

[MariosGkMeng]

I am trying to solve my own specific problem. The data.sampler.boundary_condition contains code for Dirichlet and Periodic boundary conditions.

It is not clear to me how one can add custom boundary conditions in the form of functions, such as:

p(0, t) = a

The tutorial does not include this scenario, neither the train.py files for any of the provided examples.

I suppose I should build this function inside boundary_condition.py?