init(log_dir=None, comment='', purge_step=None, max_queue=10, flush_secs=120, filename_suffix='')
  Creates a *SummaryWriter* that will write out events and
  summaries to the event file.

  Parameters:
     * **log_dir** (*str*) -- Save directory location. Default is
       runs/**CURRENT_DATETIME_HOSTNAME**, which changes after
       each run. Use hierarchical folder structure to compare
       between runs easily. e.g. pass in 'runs/exp1', 'runs/exp2',
       etc. for each new experiment to compare across them.

     * **comment** (*str*) -- Comment log_dir suffix appended to
       the default "log_dir". If "log_dir" is assigned, this
       argument has no effect.

     * **purge_step** (*int*) -- When logging crashes at step T+X
       and restarts at step T, any events whose global_step larger
       or equal to T will be purged and hidden from TensorBoard.
       Note that crashed and resumed experiments should have the
