Add pass descriptions

docs/optimizer/optimize.md

@@ -38,7 +38,7 @@ The `onnxscript.optimizer.optimize` call takes in several optional parameters th
 
 ```
 
-## Description of pattern rewrite rules applied by `onnxscript.optimizer.optimize`
+## List of pattern rewrite rules applied by `onnxscript.optimizer.optimize`
 
 ```{eval-rst}
 .. autosummary::

onnxscript/optimizer/constant_folding.py

@@ -263,7 +263,10 @@ def fold_constants(
     *,
     onnx_shape_inference: bool = False,
 ) -> bool:
-    """Returns true iff the model was modified."""
+    """
+    Applies constant folding optimization to the model.
+    Returns true iff the model was modified.
+    """
     folder = ConstantFolder(
         evaluator.registry,
         external_data_folder,

onnxscript/optimizer/copy_propagation.py

@@ -68,13 +68,15 @@ def visit_node(self, node: onnx.NodeProto) -> None:
 
 
 def do_copy_propagation(model: onnx.ModelProto, *, remove_unused: bool = True) -> None:
+    """Applies copy propagation optimization to the model."""
     transformer = CopyPropagator()
     transformer.visit_model(model)
     if remove_unused:
         onnxscript.optimizer.remove_unused_nodes(model)
 
 
 def do_sequence_simplification(model: onnx.ModelProto, *, remove_unused: bool = True) -> None:
+    """Simplifies Sequence based ops (SequenceConstruct, ConcatFromSequence) present in the model."""
     transformer = SymbolicEvaluator()
     transformer.visit_model(model)
     if remove_unused:

onnxscript/optimizer/simple_function_folding.py

@@ -200,6 +200,7 @@ def function_with_unused_outputs(self) -> dict[ir.FunctionId, onnx.FunctionProto
 
 
 def inline_simple_functions(model: onnx.ModelProto, node_count: int = 2) -> bool:
+    """Inlines simple functions based on a node count threshold"""
     inliner = FunctionInliner(node_count)
     inliner.visit_model(model)
     logger.info(
@@ -218,6 +219,7 @@ def inline_simple_functions(model: onnx.ModelProto, node_count: int = 2) -> bool
 
 
 def inline_functions_with_unused_outputs(model: onnx.ModelProto) -> bool:
+    """Inlines function nodes that have unused outputs."""
     # TODO: Use onnx.inliner after 1.16.
     # This visitor based inliner is used to ensure the function inner value info remains consistent.
     visitor = FindFunctionWithUnusedOutputsVisitor()