docs: def _get_format(self, request):
          """
          Determine and return a 'formats.Format' instance describing the most desired response format
          that is supported by these views.
  
          :param request: A django.http.HttpRequest instance.
  
          Formats specified by extension (e.g. '/articles/index.html') take precedence over formats
          given in the HTTP Accept header, even if it's a format that isn't known by Respite.
  
          If the request doesn't specify a format by extension (e.g. '/articles/' or '/articles/new')
          and none of the formats in the HTTP Accept header are supported, Respite will fall back
          on the format given in DEFAULT_FORMAT.
          """
  
          # Derive a list of 'formats.Format' instances from the list of formats these views support.
          supported_formats = [formats.find(format) for format in self.supported_formats]
  
          # Determine format by extension...
          if '.' in request.path:
              extension = request.path.split('.')[-1]
  
              try:
                  format = formats.find_by_extension(extension)
              except formats.UnknownFormat:
                  return None
  
              if format in supported_formats:
                  return format
              else:
                  return None
  
          # Determine format by HTTP Accept header...
          if 'HTTP_ACCEPT' in request.META:
              content_types = parse_http_accept_header(request.META['HTTP_ACCEPT'])
  
              # Only consider 'accept' headers with a single format in an attempt to play nice
              # with browsers that ask for formats they really should not want.
              if len(content_types) == 1:
                  content_type = content_types[0]
  
                  # If the request has no preference as to the format of its response, prefer the
                  # first of the view's supported formats.
                  if content_type == '*/*':
                      return supported_formats[0]
  
                  try:
                      format = formats.find_by_content_type(content_type)
                  except formats.UnknownFormat:
                      return None
  
                  if format in supported_formats:
                      return format
                  else:
                      return None
  
          # If no format is given by either extension or header, default to the format given in
          # RESPITE_DEFAULT_FORMAT (given, of course, that it's supported by the view).
          if DEFAULT_FORMAT:
              format = formats.find(DEFAULT_FORMAT)
  
              if format in supported_formats:
                  return format
              else:
                  return None