code: def DocbookXslt(env, target, source=None, *args, **kw):
      
      # Init list of targets/sources
      target, source = __extend_targets_sources(target, source)
      
      # Init XSL stylesheet
      kw['DOCBOOK_XSL'] = kw.get('xsl', 'transform.xsl')
  
      # Setup builder
      __builder = __select_builder(__lxml_builder, __libxml2_builder, __xsltproc_builder)
      
      # Create targets
      result = []
      for t,s in zip(target,source):
          r = __builder.__call__(env, t, s, **kw)
          env.Depends(r, kw['DOCBOOK_XSL'])
          result.extend(r)
  
      return result
docs: A pseudo-Builder, applying a simple XSL transformation to the input file.