When I want to script a method which calls torch.nn.dropout, it comes up a error message:
RuntimeError: 
unknown builtin op:
    """
    Chunking.

    Parameters
    ----------
    z_in : ``torch.LongTensor``, required.
       The output of the character-level lstms.
    """

    z_in = self.drop_(z_in)
           ~~~~~~~~~ <--- HERE

    out = self.chunk_layer(z_in).squeeze(1)

    return out

self.drop = torch.nn.Dropout(p=droprate)

@torch.jit.script
     def chunking(self, z_in):
         """
         Chunking.
 
         Parameters
         ----------
         z_in : ``torch.LongTensor``, required.
            The output of the character-level lstms.
         """
 
         z_in = self.drop(z_in)
 
         out = self.chunk_layer(z_in).squeeze(1)
 
         return out