class_docstr: Base class for cascade decode head used in
  :class:`CascadeEncoderDecoder.
docstr: Placeholder of forward function.
docstr_tok: ["Placeholder","of","forward","function","."]
code: def forward(self, inputs, prev_output):
      """Placeholder of forward function."""
      pass
  
file_path: lavis/lavis/common/annotator/uniformer/mmseg/models/decode_heads/cascade_decode_head.py
imports: from abc import ABCMeta, abstractmethod
  from .decode_head import BaseDecodeHead
label_desc: Use image node_id 2 for calling the BaseCascadeDecodeHead obj's underlying member method code with example usage: obj.forward(inputs, prev_output) without return types