class_docstr: Portal input for monkey-patching of mask in predict mode.
code: def forward(self, x):
      if isinstance(x, (list, tuple)):
          x = x[0]
      self.state = (x,)
      return x
  
imports: import functools
  from trax import layers
  from trax.fastmath import numpy
  from trax.models.reformer import reformer
  from trax.models.research import configurable_transformer
  from trax.models.research import transformer2
label_desc: Use image node_id 2 for calling the _PortalInput obj's underlying member method code with example usage: obj.forward(x) and returns: x