class_docstr: Generic merge layer for elementwise merge functions.
  
  Used to implement `Sum`, `Average`, etc.
code: def compute_output_shape(self, input_shape):
      if input_shape[0] is None:
          output_shape = None
      else:
          output_shape = input_shape[0][1:]
      for i in range(1, len(input_shape)):
          if input_shape[i] is None:
              shape = None
          else:
              shape = input_shape[i][1:]
          output_shape = self._compute_elemwise_op_output_shape(
              output_shape, shape
          )
      batch_sizes = {s[0] for s in input_shape if s is not None} - {
          None
      }
      if len(batch_sizes) == 1:
          output_shape = (list(batch_sizes)[0],) + output_shape
      else:
          output_shape = (None,) + output_shape
      return output_shape
  
imports: from tensorflow.python.keras import backend
  from tensorflow.python.keras.engine import base_layer_utils
  from tensorflow.python.keras.engine.base_layer import Layer
  from tensorflow.python.keras.utils import tf_utils
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import array_ops_stack
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn
label_desc: Use image node_id 6 for calling the _Merge obj's underlying member method code with example usage: obj.compute_output_shape(input_shape) and returns: output_shape