InitExcitVecs Subroutine

    subroutine InitExcitVecs(session)
        implicit none
        type(ExcitGenSessionType), intent(inout) :: session
        call DestructExcitVecs(session)
        allocate(session%elecIndices(session%rank))
        allocate(session%holeIndices(session%rank))
        ! to indicate initialised indices
        session%elecIndices(1) = 0
        session%holeIndices(1) = 0
        allocate(session%elecSpinOrbs(session%rank))
        allocate(session%holeSpinOrbs(session%rank))
    end subroutine InitExcitVecs