class_docstr: Waterfall plot
code: def __init__(self, layout, histogram_layout=None):
      if not isinstance(layout, pg.GraphicsLayoutWidget):
          raise ValueError(
              "layout must be instance of pyqtgraph.GraphicsLayoutWidget"
          )
  
      if histogram_layout and not isinstance(
          histogram_layout, pg.GraphicsLayoutWidget
      ):
          raise ValueError(
              "histogram_layout must be instance of pyqtgraph.GraphicsLayoutWidget"
          )
  
      self.layout = layout
      self.histogram_layout = histogram_layout
  
      self.history_size = 100
      self.counter = 0
  
      self.create_plot()
  
imports: import collections, math
  from Qt import QtCore
  import pyqtgraph
label_desc: Use image node_id 1 to create a new WaterfallPlotWidget object  with example: obj = WaterfallPlotWidget(layout, histogram_layout)