Tensorflow: scalar_summary duplicate exception - tensorboard

Question

I'm following the tensorboard tutorial in order to learn how to use summaries and I keep getting the error below.
It throws the error while calling:
summary_op = tf.merge_all_summaries()
but the problem, seems to be here:
def variable_summaries(var):
with tf.name_scope('summaries'):
mean = tf.reduce_mean(var)
tf.scalar_summary('mean', mean)
Any clues why is this happening?
InvalidArgumentError (see above for traceback): Duplicate tag mean
found in summary inputs [[Node: MergeSummary/MergeSummary =
MergeSummary[N=7,
_device="/job:localhost/replica:0/task:0/cpu:0"](layer1/weights/summaries/ScalarSummary,
layer1/biases/summaries/ScalarSummary,
layer2/weights/summaries/ScalarSummary,
layer2/biases/summaries/ScalarSummary,
out/weights/summaries/ScalarSummary,
out/biases/summaries/ScalarSummary, ScalarSummary)]]

Answer 1

The problem is on the source where I got the code. The tensorboard link takes us to the master version where the code is wrong:
def variable_summaries(var):
"""Attach a lot of summaries to a Tensor (for TensorBoard visualization)."""
with tf.name_scope('summaries'):
mean = tf.reduce_mean(var)
tf.summary.scalar('mean', mean)
with tf.name_scope('stddev'):
stddev = tf.sqrt(tf.reduce_mean(tf.square(var - mean)))
tf.summary.scalar('stddev', stddev)
tf.summary.scalar('max', tf.reduce_max(var))
tf.summary.scalar('min', tf.reduce_min(var))
tf.summary.histogram('histogram', var)
The other versions have the following, correct, code:
def variable_summaries(var, name):
"""Attach a lot of summaries to a Tensor."""
with tf.name_scope('summaries'):
mean = tf.reduce_mean(var)
tf.scalar_summary('mean/' + name, mean)
with tf.name_scope('stddev'):
stddev = tf.sqrt(tf.reduce_mean(tf.square(var - mean)))
tf.scalar_summary('stddev/' + name, stddev)
tf.scalar_summary('max/' + name, tf.reduce_max(var))
tf.scalar_summary('min/' + name, tf.reduce_min(var))
tf.histogram_summary(name, var)