user.getIdTokenResult().then(({ token, signInProvider, claims })=>{
  const info = claims.firebase;
  const [id] = info?.identities[signInProvider || ''];
  consoel.log('Here is my id', id);
});

{
  aud: "####",
  auth_time: 123456,
  exp: 123456,
  firebase: {
    identities: { twitter.com: ["ID"] },
    sign_in_provider: "twitter.com",
  },
  iat: 123456,
  ...
}

/**
 * Interface representing a parsed ID token.
 *
 * @privateRemarks TODO(avolkovi): consolidate with parsed_token in implementation.
 *
 * @public
 */
export declare interface ParsedToken {
    /** Expiration time of the token. */
    'exp'?: string;
    /** UID of the user. */
    'sub'?: string;
    /** Time at which authentication was performed. */
    'auth_time'?: string;
    /** Issuance time of the token. */
    'iat'?: string;
    /** Firebase specific claims, containing the provider(s) used to authenticate the user. */
    'firebase'?: {
        'sign_in_provider'?: string;
        'sign_in_second_factor'?: string;
    };
    /** Map of any additional custom claims. */
    [key: string]: string | object | undefined;
}

export declare interface ParsedToken {
    /* ... */
    'iat'?: string;
    /** Firebase specific claims, containing the provider(s) used to authenticate the user. */
    'firebase'?: {
        identities: {
          [key: string]: Array<IdTypeOfSomething>
        };
        'sign_in_provider'?: string;
        'sign_in_second_factor'?: string;
    };
    /** Map of any additional custom claims. */
    [key: string]: string | object | undefined;
}

export declare interface IdTokenResult {
    /**
     * The authentication time formatted as a UTC string.
     *
     * @remarks
     * This is the time the user authenticated (signed in) and not the time the token was refreshed.
     */
    authTime: string;
    /** The ID token expiration time formatted as a UTC string. */
    expirationTime: string;
    /** The ID token issuance time formatted as a UTC string. */
    issuedAtTime: string;
    /**
     * The sign-in provider through which the ID token was obtained (anonymous, custom, phone,
     * password, etc).
     *
     * @remarks
     * Note, this does not map to provider IDs.
     */
    signInProvider: string | null;
    /**
     * The type of second factor associated with this session, provided the user was multi-factor
     * authenticated (eg. phone, etc).
     */
    signInSecondFactor: string | null;
    /** The Firebase Auth ID token JWT string. */
    token: string;
    /**
     * The entire payload claims of the ID token including the standard reserved claims as well as
     * the custom claims.
     */
    claims: ParsedToken;
}

interface IdTokenResult {
  /* ... */
  claims: {
    [key: string]: any;
  };
}