code: def plot_centres(array, centres, units, kpc_per_arcsec, zoom_offset_arcsec):
      
      if centres is not None:
  
          colors = itertools.cycle(["m", "y", "r", "w", "c", "b", "g", "k"])
  
          for centres_of_galaxy in centres:
              color = next(colors)
              for centre in centres_of_galaxy:
  
                  if zoom_offset_arcsec is not None:
                      centre -= zoom_offset_arcsec
  
                  centre_units = convert_grid_units(array=array, grid_arcsec=centre, units=units,
                                                    kpc_per_arcsec=kpc_per_arcsec)
                  plt.scatter(y=centre_units[0], x=centre_units[1], s=300, c=color, marker='x')
docs: Plot the (y,x) centres (e.g. of a mass profile) on the array as an 'x'.
  
      Parameters
      -----------
      array : data.array.scaled_array.ScaledArray
          The 2D array of data which is plotted.
      centres : [[tuple]]
          The list of centres; centres in the same list entry are colored the same.
      units : str
          The units of the y / x axis of the plots, in arc-seconds ('arcsec') or kiloparsecs ('kpc').
      kpc_per_arcsec : float or None
          The conversion factor between arc-seconds and kiloparsecs, required to plot the units in kpc.