docs: def find(self, package, **kwargs):
          """
          Find method.
  
          Args:
              package (str): package to find.
              **kwargs (): additional keyword arguments.
  
          Returns:
              PackageSpec: the PackageSpec corresponding to the package, or None.
          """
          spec = find_spec(package)
          if spec is None:
              return None
          limit = []
          if '.' in package:
              package, limit = package.split('.', 1)
              limit = [limit]
              spec = find_spec(package)
          if spec is not None:
              if spec.submodule_search_locations:
                  path = spec.submodule_search_locations[0]
              elif spec.origin and spec.origin != 'built-in':
                  path = spec.origin
              else:
                  return None
              return PackageSpec(spec.name, path, limit)
          return None