code: def plotSpectrum(pfreq, pmagn, signalname):
      fig = figure(figsize=(8, 5), dpi=80, facecolor="w", edgecolor="k")
      title = "Spectrum " + str(signalname)
      fig.suptitle(title)
      plot(pfreq * fs / 2, pmagn)
      figname = title + ".png"
      fig.savefig(figname)
      html_ = '<p><img src="' + figname + '"></p>\n'
      close("all")
      return html_
  
file_path: essentia/test/src/qa/hpcp/test_hpcp_plots.py
imports: import numpy
  import essentia
  from essentia.standard import *
  from matplotlib.pyplot import imshow, show, plot, title, ylim, legend, figure, grid, GridSpec, subplot, text, tight_layout, yticks, locator_params, close
  import matplotlib.pyplot
  from test_hpcp_parameters import *
  from test_hpcp_extract import *
label_desc: Use image node_id 1 for calling a global function with example usage: plotSpectrum(pfreq, pmagn, signalname) and returns: html_