initialize_integration_class_6d Subroutine

    subroutine initialize_integration_class_6d(me,fxyzqrs,&
                                               xl,xu,yl,yu,zl,zu,ql,qu,rl,ru,sl,su,&
                                               tolx,toly,tolz,tolq,tolr,tols,&
                                               methodx,methody,methodz,methodq,methodr,methods)

    implicit none

    class(integration_class_6d),intent(inout) :: me
    procedure(func_6d)     :: fxyzqrs  !! 6d function: f(x,y,z,q,r,s)
    real(wp),intent(in)    :: xl       !! x integration lower bound
    real(wp),intent(in)    :: xu       !! x integration upper bound
    real(wp),intent(in)    :: yl       !! y integration lower bound
    real(wp),intent(in)    :: yu       !! y integration upper bound
    real(wp),intent(in)    :: zl       !! z integration lower bound
    real(wp),intent(in)    :: zu       !! z integration upper bound
    real(wp),intent(in)    :: ql       !! q integration lower bound
    real(wp),intent(in)    :: qu       !! q integration upper bound
    real(wp),intent(in)    :: rl       !! r integration lower bound
    real(wp),intent(in)    :: ru       !! r integration upper bound
    real(wp),intent(in)    :: sl       !! s integration lower bound
    real(wp),intent(in)    :: su       !! s integration upper bound
    real(wp),intent(in)    :: tolx     !! error tolerance for dx integration
    real(wp),intent(in)    :: toly     !! error tolerance for dy integration
    real(wp),intent(in)    :: tolz     !! error tolerance for dz integration
    real(wp),intent(in)    :: tolq     !! error tolerance for dq integration
    real(wp),intent(in)    :: tolr     !! error tolerance for dr integration
    real(wp),intent(in)    :: tols     !! error tolerance for ds integration
    integer,intent(in)     :: methodx  !! quadrature method to use for x
    integer,intent(in)     :: methody  !! quadrature method to use for y
    integer,intent(in)     :: methodz  !! quadrature method to use for z
    integer,intent(in)     :: methodq  !! quadrature method to use for q
    integer,intent(in)     :: methodr  !! quadrature method to use for r
    integer,intent(in)     :: methods  !! quadrature method to use for s

    procedure(func_1d),pointer :: dummy => null() !! these will be set in [[integrate_3d]]

    me%fxyzqrs => fxyzqrs  !the user-defined f(x,y,z,q,r,s) function to integrate

    ! individual integrators:
    call me%ix%initialize(dummy,xl,xu,tolx,methodx)
    call me%iy%initialize(dummy,yl,yu,toly,methody)
    call me%iz%initialize(dummy,zl,zu,tolz,methodz)
    call me%iq%initialize(dummy,ql,qu,tolq,methodq)
    call me%ir%initialize(dummy,rl,ru,tolr,methodr)
    call me%is%initialize(dummy,sl,su,tols,methods)

    end subroutine initialize_integration_class_6d