docs: function signout (idToken, postLogoutRedirectUri) {
    if (!idToken) {
      return Promise.reject(new Error('ID Token required for signout'))
    }
    var params = {}
    params.id_token_hint = idToken
    if (postLogoutRedirectUri) {
      params.post_logout_redirect_uri = postLogoutRedirectUri
    }
    var options = {
      endpoint: 'signout'
    }
    var uri = this.authorizationUri(options)
    var self = this
    var requestOptions = {
      url: uri,
      method: 'POST',
      json: params,
      agentOptions: self.agentOptions
    }
    if (self.proxy) {
      requestOptions.proxy = self.proxy
    }
  
    return Promise.resolve()
      .then(function () {
        return request(requestOptions)
      })
  }