class_docstr: Main spectrum plot
docstr: Clear spectrum persistence curves
docstr_tok: ["Clear","spectrum","persistence","curves"]
code: def clear_persistence(self):
      """Clear spectrum persistence curves"""
      self.persistence_data = None
      for curve in self.persistence_curves:
          curve.clear()
          self.plot.removeItem(curve)
      self.create_persistence_curves()
  
imports: import collections, math
  from Qt import QtCore
  import pyqtgraph
label_desc: Use image node_id 27 for calling the SpectrumPlotWidget obj's underlying member method code with example usage: obj.clear_persistence() without return types