title: What is Bijectors in layman terms in tensorflow probability
body: <p>I am not able to understand Bijectors in Tensorflow-probability.
  how to use them. </p>
  
  <pre class="lang-py prettyprint-override"><code>standard_gumbel = tfd.TransformedDistribution(
  distribution=tfd.Exponential(rate=1.),
  bijector=tfb.Chain([
  tfb.Affine(
  scale_identity_multiplier=-1.,
  event_ndims=0),
  tfb.Invert(tfb.Exp()),
  ]))
  </code></pre>