class_docstr: A flattening block.
  
  :param in_keys: One key identifying the input tensors.
  :param out_keys: One key identifying the output tensors.
  :param in_shapes: List of input shapes.
  :param num_flatten_dims: the number of dimensions to flatten out (from right).
code: def __repr__(self):
      txt = FlattenBlock.__name__
      txt += f"\n\tnum_flatten_dims: {self.num_flatten_dims}"
      txt += f"\n\tOut Shapes: {self.out_shapes()}"
      return txt
  
file_path: maze/maze/perception/blocks/general/flatten.py
imports: from typing import Union, List, Sequence, Dict
  import torch
  from maze.core.annotations import override
  from maze.perception.blocks.base import PerceptionBlock
label_desc: Use image node_id 3 for calling the FlattenBlock obj's underlying member method code with example usage: obj.__repr__() and returns: txt