code: def _adjust(hsl, attribute, percent):
      """Internal adjust function"""
      hsl = list(hsl)
      if attribute > 0:
          hsl[attribute] = _clamp(hsl[attribute] + percent)
      else:
          hsl[attribute] += percent
  
      return hsl
  
file_path: pygal/pygal/colors.py
imports: from __future__ import division
label_desc: Use image node_id 7 for calling a global function with example usage: _adjust(hsl, attribute, percent) and returns: hsl