code: function () {
          var binding = getBinding(this.props);
          if (binding) {
            if (binding instanceof Binding) {
              return binding;
            } else if (typeof binding === 'object') {
              var keys = Object.keys(binding);
              return keys.length === 1 ? binding[keys[0]] : binding['default'];
            }
          } else {
            return this.observedBindings && this.observedBindings[0];
          }
        }
docs: Get default component state binding. Use this to get component's binding.
  <p>Default binding is single binding for single-binding components or
  binding with key 'default' for multi-binding components or else first observed binding, if any.
  This method allows smooth migration from single to multi-binding components, e.g. you start with:
  <pre><code>{ binding: foo }</code></pre>
  or
  <pre><code>{ binding: { default: foo } }</code></pre>
  or even
  <pre><code>{ binding: { any: foo } }</code></pre>
  and add more bindings later:
  <pre><code>{ binding: { default: foo, aux: auxiliary } }</code></pre>
  This way code changes stay minimal.
  @return {Binding} default component state binding