code: def pearson_correlation_coefficient(predictions, labels, weights_fn=None):
    
    del weights_fn
    _, pearson = tf.contrib.metrics.streaming_pearson_correlation(predictions,
                                                                  labels)
    return pearson, tf.constant(1.0)
docs: Calculate pearson correlation coefficient.
  
    Args:
      predictions: The raw predictions.
      labels: The actual labels.
      weights_fn: Weighting function.
  
    Returns:
      The pearson correlation coefficient.