Add DiffSL export functionality

CHANGELOG.md

@@ -5,6 +5,7 @@
 - Improve the performance of matrix multiplication with CasADi expressions. ([#5351](https://github.com/pybamm-team/PyBaMM/pull/5351))
 - Adds option for lists of inputs to `solve` to include input parameters which are used
 as initial conditions. ([#5311](https://github.com/pybamm-team/PyBaMM/pull/5311))
+- DiffSL export for discretised PyBaMM models. ([#5370](https://github.com/pybamm-team/PyBaMM/pull/5370))
 
 ## Bug fixes
 

pyproject.toml

@@ -101,6 +101,8 @@ dev = [
     "importlib-metadata; python_version < '3.10'",
     # For property based testing
     "hypothesis",
+    # For diffsl tests
+    "pydiffsol",
 ]
 jax = ["jax>=0.4.36,<0.7.0"]
 # Contains all optional dependencies, except for jax, and dev dependencies

src/pybamm/__init__.py

@@ -67,6 +67,9 @@
 from .models.event import Event
 from .models.event import EventType
 
+# DiffSL export
+from .expression_tree.operations.diffsl import DiffSLExport
+
 # Battery models
 from .models.full_battery_models.base_battery_model import (
     BaseBatteryModel,