Retrieves the session from the EIS uniquely identified by the specified
{@code sessionId}.
@param sessionId the system-wide unique identifier of the Session object to retrieve from
the EIS.
@return the persisted session in the EIS identified by {@code sessionId}.
@throws UnknownSessionException if there is no EIS record for any session with the
specified {@code sessionId}
Retrieves the session from the EIS uniquely identified by the specified {@code sessionId}.
@param sessionId the system-wide unique identifier of the Session object to retrieve from the EIS. @return the persisted session in the EIS identified by {@code sessionId}. @throws UnknownSessionException if there is no EIS record for any session with the specified {@code sessionId}