<p>List of <a href="${link build-ref#labels}">labels</a>;
  <a href="#configurable-attributes">nonconfigurable</a>; default is the package's
  <code><a href="${link package.default_package_metadata}">default_package_metadata</a></code>
</p>

<p>
A list of labels that are associated metadata about this target.
Typically, the labels are simple rules that return a provider of
constant values. Rules and aspects may use these labels to perform some
additional analysis on the build graph.
</p>

<p>
The canonical use case is that of
<a href="https://github.com/bazelbuild/rules_license">rules_license</a>.
For that use case, <code>package_metadata</code> and
<code>default_package_metadata</code> is used to attach information
about a package's licence or version to targets. An aspect applied
to a top-level binary can be used to gather those and produce
compliance reports.
</p>
