docs: def insert_json(table=None,
                  bulk_size=1000,
                  concurrency=25,
                  hosts=None,
                  output_fmt=None):
      """Insert JSON lines fed into stdin into a Crate cluster.
  
      If no hosts are specified the statements will be printed.
  
      Args:
          table: Target table name.
          bulk_size: Bulk size of the insert statements.
          concurrency: Number of operations to run concurrently.
          hosts: hostname:port pairs of the Crate nodes
      """
      if not hosts:
          return print_only(table)
  
      queries = (to_insert(table, d) for d in dicts_from_stdin())
      bulk_queries = as_bulk_queries(queries, bulk_size)
      print('Executing inserts: bulk_size={} concurrency={}'.format(
          bulk_size, concurrency), file=sys.stderr)
  
      stats = Stats()
      with clients.client(hosts, concurrency=concurrency) as client:
          f = partial(aio.measure, stats, client.execute_many)
          try:
              aio.run_many(f, bulk_queries, concurrency)
          except clients.SqlException as e:
              raise SystemExit(str(e))
      try:
          print(format_stats(stats.get(), output_fmt))
      except KeyError:
          if not stats.sampler.values:
              raise SystemExit('No data received via stdin')
          raise