code: def _get_default_bins(self):
          
          if self._default_bins is None:
              v = 1E-12
              buckets = []
              neg_buckets = []
              while v < 1E20:
                  buckets.append(v)
                  neg_buckets.append(-v)
                  v *= 1.1
              self._default_bins = neg_buckets[::-1] + [0] + buckets
          return self._default_bins
docs: Ported from the C++ function InitDefaultBucketsInner() in the following file.
          https://github.com/tensorflow/tensorflow/blob/master/tensorflow/core/lib/histogram/histogram.cc
          See the following tutorial for more details on how TensorFlow initialize bin distribution.
          https://www.tensorflow.org/programmers_guide/tensorboard_histograms