code: def forward(self, x, mask=None):
      for layer in self.layers:
          x = layer(x, mask=mask)
      return x
  
imports: import copy
  import math
  import torch
  import torch.nn
  import torch.nn.functional
  from stanza.models.constituency.positional_encoding import ConcatSinusoidalEncoding
label_desc: Use image node_id 2 for calling the PartitionedTransformerEncoder obj's underlying member method code with example usage: obj.forward(x, mask) and returns: x