class_docstr: Module divides a histogram along first axis encountered, eg. time.
  
  For example, split histogram time:x:y along time axis.
  This will produce a data-frame summarizing the split information,
  where time is the index and each row is a x:y histogram.
code: def update_divided(self, divided, split, yname):
      if self.flatten_output:
          divided.update(split)
      else:
          divided[yname] = [
              {self.index_col: k, self.hist_col: h}
              for k, h in split.items()
          ]
      return divided
  
file_path: popmon/popmon/hist/hist_splitter.py
imports: import pandas
  from popmon.base import Module
  from popmon.hist.hist_utils import get_histogram, is_timestamp, split_hist_along_first_dimension
label_desc: Use image node_id 3 for calling the HistSplitter obj's underlying member method code with example usage: obj.update_divided(divided, split, yname) and returns: divided