Simplify the code for getting multiple items

Signed-off-by: DarkLight1337 <[email protected]>

vllm/multimodal/inputs.py

@@ -273,7 +273,7 @@ def build_elems(
         self,
         key: str,
         batch: NestedTensors,
-    ) -> list[MultiModalFieldElem]:
+    ) -> Sequence[MultiModalFieldElem]:
         field = self.field_cls(key=key, modality=self.modality)
         return field.build_elems(batch, **self.field_config)  # type: ignore
 
@@ -285,7 +285,7 @@ class MultiModalKwargsItem(UserDict[str, MultiModalFieldElem]):
     """
 
     @staticmethod
-    def from_elems(elems: list[MultiModalFieldElem]) -> "MultiModalKwargsItem":
+    def from_elems(elems: Sequence[MultiModalFieldElem]):
         return MultiModalKwargsItem({elem.field.key: elem for elem in elems})
 
     @property
@@ -304,7 +304,7 @@ class MultiModalKwargs(UserDict[str, NestedTensors]):
 
     The metadata :code:`items` enables us to obtain the keyword arguments
     corresponding to each data item in :class:`MultiModalDataItems`, via
-    :meth:`get_num_items` and :meth:`get_item`.
+    :meth:`get_item` and :meth:`get_items`.
     """
 
     @staticmethod
@@ -314,7 +314,7 @@ def from_hf_inputs(
     ):
         # NOTE: This skips fields in `hf_inputs` that are not in `config_by_key`
         # We assume that those fields are not used in vLLM
-        elems_by_key = dict[str, list[MultiModalFieldElem]]()
+        elems_by_key = dict[str, Sequence[MultiModalFieldElem]]()
         keys_by_modality = defaultdict[str, set[str]](set)
         for key, config in config_by_key.items():
             batch = hf_inputs.get(key)
@@ -342,7 +342,7 @@ def from_hf_inputs(
         return MultiModalKwargs.from_items(items)
 
     @staticmethod
-    def from_items(items: list[MultiModalKwargsItem]) -> "MultiModalKwargs":
+    def from_items(items: Sequence[MultiModalKwargsItem]):
         """Construct a new :class:`MultiModalKwargs` from multiple items."""
         elems_by_key = defaultdict[str, list[MultiModalFieldElem]](list)
         for item in items:
@@ -453,32 +453,38 @@ def __eq__(self, other: object) -> bool:
         return (ks == other.keys()
                 and all(nested_tensors_equal(self[k], other[k]) for k in ks))
 
-    def get_num_items(self, modality: str) -> int:
-        """Get the number of items belonging to a modality."""
+    def _validate_modality(self, method_name: str, modality: str) -> None:
         if not self._items_by_modality:
             raise RuntimeError(
-                "`get_num_items` is not supported when "
+                f"`{method_name}` is not supported when "
                 "MultiModalKwargs is not initialized with `items`")
 
+        if modality not in self._items_by_modality:
+            available_modalities = set(self._items_by_modality.keys())
+            raise KeyError(f"Modality {modality!r} not found. "
+                           f"Available modalities: {available_modalities}")
+
+    def get_item_count(self, modality: str) -> int:
+        """Get the number of items belonging to a modality."""
+        self._validate_modality("get_item_count", modality)
         return len(self._items_by_modality[modality])
 
     def get_item(self, modality: str, item_index: int) -> MultiModalKwargsItem:
         """
         Get the keyword arguments corresponding to an item identified by
         its modality and index.
         """
-        if not self._items_by_modality:
-            raise RuntimeError(
-                "`get_item` is not supported when "
-                "MultiModalKwargs is not initialized with `items`")
-
-        if modality not in self._items_by_modality:
-            available_modalities = set(self._items_by_modality.keys())
-            raise KeyError(f"Modality {modality!r} not found. "
-                           f"Available modalities: {available_modalities}")
-
+        self._validate_modality("get_item", modality)
         return self._items_by_modality[modality][item_index]
 
+    def get_items(self, modality: str) -> Sequence[MultiModalKwargsItem]:
+        """
+        Get the keyword arguments corresponding to each item belonging to
+        a modality.
+        """
+        self._validate_modality("get_items", modality)
+        return self._items_by_modality[modality]
+
 
 MultiModalPlaceholderDict = Mapping[str, Sequence[PlaceholderRange]]
 """

vllm/v1/engine/processor.py

@@ -116,10 +116,9 @@ def process_inputs(
         decoder_mm_data = decoder_inputs.multi_modal_data
         if isinstance(decoder_mm_data, MultiModalKwargs):
             precomputed_mm_inputs = [
-                MultiModalKwargs.from_items(
-                    [decoder_mm_data.get_item(modality, item_idx)])
+                MultiModalKwargs.from_items([item])
                 for modality in decoder_mm_data.modalities
-                for item_idx in range(decoder_mm_data.get_num_items(modality))
+                for item in decoder_mm_data.get_items(modality)
             ]
 
         # Apply MM mapper