class_docstr: Main spectrum plot
docstr: Create main spectrum plot
docstr_tok: ["Create","main","spectrum","plot"]
code: def create_plot(self):
      """Create main spectrum plot"""
      self.posLabel = self.layout.addLabel(
          row=0, col=0, justify="right"
      )
      self.plot = self.layout.addPlot(row=1, col=0)
      self.plot.showGrid(x=True, y=True)
      self.plot.setLabel("left", "Power", units="dB")
      self.plot.setLabel("bottom", "Frequency", units="Hz")
      self.plot.setLimits(xMin=0)
      self.plot.showButtons()
  
      # self.plot.setDownsampling(mode="peak")
      # self.plot.setClipToView(True)
  
      self.create_baseline_curve()
      self.create_persistence_curves()
      self.create_average_curve()
      self.create_peak_hold_min_curve()
      self.create_peak_hold_max_curve()
      self.create_main_curve()
  
      # Create crosshair
      self.vLine = pg.InfiniteLine(angle=90, movable=False)
      self.vLine.setZValue(1000)
      self.hLine = pg.InfiniteLine(angle=0, movable=False)
      self.vLine.setZValue(1000)
      self.plot.addItem(self.vLine, ignoreBounds=True)
      self.plot.addItem(self.hLine, ignoreBounds=True)
      self.mouseProxy = pg.SignalProxy(
          self.plot.scene().sigMouseMoved,
          rateLimit=60,
          slot=self.mouse_moved,
      )
  
imports: import collections, math
  from Qt import QtCore
  import pyqtgraph
label_desc: Use image node_id 2 for calling the SpectrumPlotWidget obj's underlying member method code with example usage: obj.create_plot() without return types