def _get_default_bins(self):
        """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"""
        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
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