code: public function findPackage($name, $constraint)
      {
          foreach ($this->repositories as $repository) {
              /** @var RepositoryInterface $repository */
              if ($package = $repository->findPackage($name, $constraint)) {
                  return $package;
              }
          }
  
          return null;
      }
docs: Searches for a package by it's name and version in managed repositories.
  
  @param string                                                 $name       package name
  @param string|\Composer\Semver\Constraint\ConstraintInterface $constraint package version or version constraint to match against
  
  @return PackageInterface|null