class_docstr: Block GRU cell implementation.
  
  Deprecated: use GRUBlockCellV2 instead.
  
  The implementation is based on:  http://arxiv.org/abs/1406.1078
  Computes the GRU cell forward propagation for 1 time step.
  
  This kernel op implements the following mathematical equations:
  
  Biases are initialized with:
  
  * `b_ru` - constant_initializer(1.0)
  * `b_c` - constant_initializer(0.0)
  
  ```
  x_h_prev = [x, h_prev]
  
  [r_bar u_bar] = x_h_prev * w_ru + b_ru
  
  r = sigmoid(r_bar)
  u = sigmoid(u_bar)
  
  h_prevr = h_prev \circ r
  
  x_h_prevr = [x h_prevr]
  
  c_bar = x_h_prevr * w_c + b_c
  c = tanh(c_bar)
  
  h = (1-u) \circ c + u \circ h_prev
  ```
code: def build(self, input_shape):
      # Check if the input size exist.
      input_size = tensor_shape.dimension_value(input_shape[1])
      if input_size is None:
          raise ValueError("Expecting input_size to be set.")
  
      self._gate_kernel = self.add_variable(
          "w_ru", [input_size + self._cell_size, self._cell_size * 2]
      )
      self._gate_bias = self.add_variable(
          "b_ru",
          [self._cell_size * 2],
          initializer=init_ops.constant_initializer(1.0),
      )
      self._candidate_kernel = self.add_variable(
          "w_c", [input_size + self._cell_size, self._cell_size]
      )
      self._candidate_bias = self.add_variable(
          "b_c",
          [self._cell_size],
          initializer=init_ops.constant_initializer(0.0),
      )
  
      self.built = True
  
imports: from __future__ import absolute_import
  from __future__ import division
  from __future__ import print_function
  from tensorflow.python.framework import ops
  from tensorflow.python.framework import tensor_shape
  from tensorflow.python.keras.engine import input_spec
  from tensorflow.python.ops import array_ops
  from tensorflow.python.ops import gen_rnn_ops
  from tensorflow.python.ops import init_ops
  from tensorflow.python.ops import math_ops
  from tensorflow.python.ops import nn_ops
  from tensorflow.python.ops import rnn_cell_impl
  from tensorflow.python.util.deprecation import deprecated_args
label_desc: Use image node_id 4 for calling the GRUBlockCell obj's underlying member method code with example usage: obj.build(input_shape) without return types