code: def _add_flatten_layer(cls, node):
      shape = TensorShape()
      dim = shape.dim.add()
      dim.size = -1
  
      dim = shape.dim.add()
      dim.size = 1
      for i in node.output_shape[1:]:
          dim.size *= i
      kwargs = {"_output_shapes": [shape]}
      return Node.create("Flatten", **kwargs)
  
imports: from __future__ import absolute_import
  from __future__ import division
  import numpy
  from mmdnn.conversion.caffe.errors import ConversionError
  from mmdnn.conversion.caffe.common_graph import Node
  from mmdnn.conversion.caffe.network import DEFAULT_PADDING
  from mmdnn.conversion.caffe.utils import get_lower_case
  from mmdnn.conversion.common.IR.graph_pb2 import TensorShape
label_desc: Use image node_id 13 for calling the NodeMapper obj's underlying member method code with example usage: obj._add_flatten_layer(cls, node) and returns: Node