<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _compute_missing_deps(self, src_tgt, actual_deps):
 """Computes deps that are used by the compiler but not specified in a BUILD file. These deps are bugs waiting to happen: the code may happen to compile because the dep was brought in some other way (e.g., by some other root target), but that is obviously fragile. Note that in practice we're OK with reliance on indirect deps that are only brought in transitively. E.g., in Scala type inference can bring in such a dep subtly. Fortunately these cases aren't as fragile as a completely missing dependency. It's still a good idea to have explicit direct deps where relevant, so we optionally warn about indirect deps, to make them easy to find and reason about. - actual_deps: a map src -> list of actual deps (source, class or jar file) as noted by the compiler. Returns a tuple (missing_file_deps, missing_direct_tgt_deps) where: - missing_file_deps: a list of dep_files where src_tgt requires dep_file, and we're unable to map to a target (because its target isn't in the total set of targets in play, and we don't want to parse every BUILD file in the workspace just to find it). - missing_direct_tgt_deps: a list of dep_tgts where src_tgt is missing a direct dependency on dep_tgt but has a transitive dep on it. All paths in the input and output are absolute. """

    analyzer = self._analyzer
    def must_be_explicit_dep(dep):
      # We don't require explicit deps on the java runtime, so we shouldn't consider that
      # a missing dep.
      return (dep not in analyzer.bootstrap_jar_classfiles
              and not dep.startswith(DistributionLocator.cached().real_home))

    def target_or_java_dep_in_targets(target, targets):
      # We want to check if the target is in the targets collection
      #
      # However, for the special case of scala_library that has a java_sources
      # reference we're ok if that exists in targets even if the scala_library does not.

      if target in targets:
        return True
      elif isinstance(target, ScalaLibrary):
        return any(t in targets for t in target.java_sources)
      else:
        return False

    # Find deps that are actual but not specified.
    missing_file_deps = OrderedSet()  # (src, src).
    missing_direct_tgt_deps_map = defaultdict(list)  # The same, but for direct deps.

    targets_by_file = analyzer.targets_by_file(self.context.targets())
    buildroot = get_buildroot()
    abs_srcs = [os.path.join(buildroot, src) for src in src_tgt.sources_relative_to_buildroot()]
    for src in abs_srcs:
      for actual_dep in filter(must_be_explicit_dep, actual_deps.get(src, [])):
        actual_dep_tgts = targets_by_file.get(actual_dep)
        # actual_dep_tgts is usually a singleton. If it's not, we only need one of these
        # to be in our declared deps to be OK.
        if actual_dep_tgts is None:
          missing_file_deps.add((src_tgt, actual_dep))
        elif not target_or_java_dep_in_targets(src_tgt, actual_dep_tgts):
          # Obviously intra-target deps are fine.
          canonical_actual_dep_tgt = next(iter(actual_dep_tgts))
          if canonical_actual_dep_tgt not in src_tgt.dependencies:
            # The canonical dep is the only one a direct dependency makes sense on.
            missing_direct_tgt_deps_map[(src_tgt, canonical_actual_dep_tgt)].append(
                (src, actual_dep))

    return (list(missing_file_deps),
            list(missing_direct_tgt_deps_map.items()))