code: def distributions_route(self, request):
      
      tag = request.args.get('tag')
      run = request.args.get('run')
      try:
        (body, mime_type) = self.distributions_impl(tag, run)
        code = 200
      except ValueError as e:
        (body, mime_type) = (str(e), 'text/plain')
        code = 400
      return http_util.Respond(request, body, mime_type, code=code)
docs: Given a tag and single run, return an array of compressed histograms.