code: def get_strokes(self):
          
  
          def stroke_dict_to_css(stroke, i=None):
              """Return a css style for the given option"""
              css = [
                  '%s.series%s {\n' %
                  (self.id, '.serie-%d' % i if i is not None else '')
              ]
              for key in ('width', 'linejoin', 'linecap', 'dasharray',
                          'dashoffset'):
                  if stroke.get(key):
                      css.append('  stroke-%s: %s;\n' % (key, stroke[key]))
              css.append('}')
              return '\n'.join(css)
  
          css = []
          if self.graph.stroke_style is not None:
              css.append(stroke_dict_to_css(self.graph.stroke_style))
          for serie in self.graph.series:
              if serie.stroke_style is not None:
                  css.append(stroke_dict_to_css(serie.stroke_style, serie.index))
  
          for secondary_serie in self.graph.secondary_series:
              if secondary_serie.stroke_style is not None:
                  css.append(
                      stroke_dict_to_css(
                          secondary_serie.stroke_style, secondary_serie.index
                      )
                  )
          return '\n'.join(css)
docs: Return a css snippet containing all stroke style options