title: what is the default hidden state of GRU in KERAS?
body: <pre><code>keras.layers.GRU(units, activation='tanh', recurrent_activation='hard_sigmoid', use_bias=True, kernel_initializer='glorot_uniform', recurrent_initializer='orthogonal', bias_initializer='zeros', kernel_regularizer=None, recurrent_regularizer=None, bias_regularizer=None, activity_regularizer=None, kernel_constraint=None, recurrent_constraint=None, bias_constraint=None, dropout=0.0, recurrent_dropout=0.0, implementation=1, return_sequences=False, return_state=False, go_backwards=False, stateful=False, unroll=False)
  </code></pre>
  
  <p>I know that the initializer of input's weight is 'glorot_uniform' and the initializer of hidden stats's weight is 'orthognal' and the initializer of bias is 'zeros'.</p>
  
  <p>But I don't know the initializer of the first hidden state of GRU </p>