code: def create_bands(self):
      self.bands = self.plot.patch(
          x="band_x",
          y="band_y",
          source=self.bollinger_bands_source,
          color=self.color,
          fill_alpha=0.4,
          alpha=0.1,
          line_width=0,
      )
      self.bands.visible = self.show_bollinger_bands
  
file_path: coach/rl_coach/dashboard_components/signals.py
imports: import random
  import numpy
  from bokeh.models import ColumnDataSource
  from bokeh.palettes import Dark2
  from rl_coach.dashboard_components.globals import show_spinner, hide_spinner, current_color
  from rl_coach.utils import squeeze_list
label_desc: Use image node_id 6 for calling the Signal obj's underlying member method code with example usage: obj.create_bands() without return types