code: def resolve_authconfig(self, registry=None):
          
  
          if self.creds_store or self.cred_helpers:
              store_name = self.get_credential_store(registry)
              if store_name is not None:
                  log.debug(
                      'Using credentials store "{0}"'.format(store_name)
                  )
                  cfg = self._resolve_authconfig_credstore(registry, store_name)
                  if cfg is not None:
                      return cfg
                  log.debug('No entry in credstore - fetching from auth dict')
  
          # Default to the public index server
          registry = resolve_index_name(registry) if registry else INDEX_NAME
          log.debug("Looking for auth entry for {0}".format(repr(registry)))
  
          if registry in self.auths:
              log.debug("Found {0}".format(repr(registry)))
              return self.auths[registry]
  
          for key, conf in six.iteritems(self.auths):
              if resolve_index_name(key) == registry:
                  log.debug("Found {0}".format(repr(key)))
                  return conf
  
          log.debug("No entry found")
          return None
docs: Returns the authentication data from the given auth configuration for a
          specific registry. As with the Docker client, legacy entries in the
          config with full URLs are stripped down to hostnames before checking
          for a match. Returns None if no match was found.