Unable to set cache key from the request context

[vmitsek-amplify]

When I trying to set cache key from request context the plugin always prepends method which leads to validation error during CF stack update: Invalid mapping expression specified: method.context.authorizer.principalId]. Is that a bug or I just using wrong mapping?
AWS documentation says that path to context does not start with method

caching:
    enabled: ${self:custom.config.is_caching_enabled}
    ttlInSeconds: 900
    cacheKeyParameters:
        - name: context.authorizer.principalId

[vmitsek-amplify]

Adding mappedFrom helped

- name: integration.request.header.principalId
   mappedFrom: context.authorizer.principalId