code: def header(self):
          ''' :class:`HeaderDict` filled with request headers.
  
              HeaderDict keys are case insensitive str.title()d
          '''
          if self._header is None:
              self._header = HeaderDict()
              for key, value in self.environ.iteritems():
                  if key.startswith('HTTP_'):
                      key = key[5:].replace('_','-').title()
                      self._header[key] = value
          return self._headef header(self):
          ''' :class:`HeaderDict` filled with request headers.
  
              HeaderDict keys are case insensitive str.title()d
          '''
          if self._header is None:
              self._header = HeaderDict()
              for key, value in self.environ.iteritems():
                  if key.startswith('HTTP_'):
                      key = key[5:].replace('_','-').title()
                      self._header[key] = value
          return self._header
docs: :class:`HeaderDict` filled with request headers.
  
              HeaderDict keys are case insensitive str.title()d