Following on from #67 I I think it would be a very good thing if MuMoT models could be created and referenced in Notebooks without using Notebook cell execution numbers. At present the example Notebooks contain cells like:

%%model
$
U -> A : g_A
U -> B : g_B
A -> U : a_A
B -> U : a_B 
A + U -> A + A : r_A
B + U -> B + B : r_B
A + B -> A + U : s
A + B -> B + U : s
$

then
`

Bioscrape uses a lot of cdef'ed functions with a wrapper for python, e.g. the cdef function "simulate_model" (which cannot be called from python) wrapped with a python function "py_simulate_model". This is a little clunky, and mysterious to users who aren't familiar with Cython.

Cython has a built-in keyword "cpdef" that makes a function both typed and python-callable. Calling a cpdef function