code: def _proc_accept_header(self, request, result):
          
  
          if result:
              # Result has already been fully determined
              return
  
          try:
              accept = request.headers['accept']
          except KeyError:
              # No Accept header to examine
              return
  
          # Obtain the best-match content type and its parameters
          ctype, params = best_match(accept, self.types.keys())
  
          # Is it a recognized content type?
          if ctype not in self.types:
              return
  
          # Get the mapped ctype and version
          mapped_ctype, mapped_version = self.types[ctype](params)
  
          # Set the content type and version
          if mapped_ctype:
              result.set_ctype(mapped_ctype, ctype)
          if mapped_version:
              result.set_version(mapped_version)
docs: Process the Accept header rules for the request.  Both the
          desired API version and content type can be determined from
          those rules.
  
          :param request: The Request object provided by WebOb.
          :param result: The Result object to store the results in.