Verifies a Firebase App Check token.

Parameters:

• token – A token from App Check.

• app – An App instance (optional).

Returns:

The token’s decoded claims.

Return type:

Dict[str, Any]

Raises:

• ValueError – If the app’s project_id is invalid or unspecified,

• or if the token's headers or payload are invalid. –

• PyJWKClientError – If PyJWKClient fails to fetch a valid signing key.