problem with external subroutine when interfaced

[Dhiraj Kumar Hazra]

Hello:
I am facing a problem. The f90wrap is not making wrapper for the subroutines that has interfaced another subroutine. For example, I have tried odeint from the following pdf

https://homepage.univie.ac.at/mario.barbatti/papers/NRF/bookf90pdf/chap16f9.pdf

SUBROUTINE derivs(x,y,dydx)
USE nrtype
IMPLICIT NONE
REAL(SP), INTENT(IN) :: x
REAL(SP), DIMENSION(:), INTENT(IN) :: y
REAL(SP), DIMENSION(:), INTENT(OUT) :: dydx
END SUBROUTINE derivs

derivs is interfaced here. If I keep it, it does not produce the wrapper. If I write external derivs, it treats derivs as a float and I get problem in executing f2py-f90wrap step.

Do you have any suggestions ?
This type of routines are not provided in examples.

Thanks in advance,
Dhiraj