code: def sigmoid_cross_entropy(output, target, name=None):
      
      return tf.reduce_mean(tf.nn.sigmoid_cross_entropy_with_logits(labels=target, logits=output), name=name)
docs: Sigmoid cross-entropy operation, see ``tf.nn.sigmoid_cross_entropy_with_logits``.
  
      Parameters
      ----------
      output : Tensor
          A batch of distribution with shape: [batch_size, num of classes].
      target : Tensor
          A batch of index with shape: [batch_size, ].
      name : string
          Name of this loss.