unt" : n,             (numeric) Size of the window in number of blocks
  "window_interval" : n,                (numeric, optional) The elapsed time in the window in seconds. Only returned if "window_block_count" is > 0
  "window_tx_count" : n,                (numeric, optional) The number of transactions in the window. Only returned if "window_block_count" is > 0 and if txcount exists for the start and end of the window.
  "txrate" : n                          (numeric, optional) The average rate of transac