code: def html(self, diff, f):
          
          env = Environment(loader=PackageLoader('clan', 'templates'))
  
          template = env.get_template('diff.html')
  
          def number_class(v):
              if v is None:
                  return ''
  
              if v > 0:
                  return 'positive'
              elif v < 0:
                  return 'negative'
  
              return ''
  
          context = {
              'diff': diff,
              'GLOBAL_ARGUMENTS': GLOBAL_ARGUMENTS,
              'format_comma': format_comma,
              'format_duration': format_duration,
              'number_class': number_class
  
          }
  
          f.write(template.render(**context).encode('utf-8'))
docs: Generate a text report for a diff.