[f2py] Create array in Python, deallocate in Fortran

When I create an array in Python, then deallocate it in Fortran, it
doesn't appear to do anything to the original Python array. Here is
the code:

helloworld.f90:

module mymodule
    real(8),allocatable,dimension(:,:)::b
    subroutine foo()
        deallocate(b)
        write(*,*) allocated(b)
    end subroutine foo2
end module mymodule


Python:

import helloworld

arr=np.array([[1,2],[3,4]],dtype=np.float64,order='F')
Out[2]:
array([[ 1.,  2.],
       [ 3.,  4.]])

helloworld.mymodule.b=arr
Out[6]:
array([[ 1.,  2.],
       [ 3.,  4.]])

helloworld.mymodule.foo()
Out: F

arr
Out[2]:
array([[ 1.,  2.],
       [ 3.,  4.]])

Fortran thinks it has deallocated b, but Python still has the original
array. I've included the directive -DF2PY_REPORT_ON_ARRAY_COPY=2, and
it doesn't give any array copy warnings.

How can I understand this behaviour? Is it potentially dangerous to
deallocate from Fortran?

-- 
Benjamin D. Forbes
School of Physics
The University of Melbourne
Parkville, VIC 3010, Australia