[ENH] create ListData

abl/structures/list_data.py

@@ -6,6 +6,8 @@ from typing import Any, List, Union
 import numpy as np
 import torch
 
+from ..utils import flatten as flatten_list
+from ..utils import to_hashable
 from .base_data_element import BaseDataElement
 
 BoolTypeTensor = Union[torch.BoolTensor, torch.cuda.BoolTensor]
@@ -293,6 +295,22 @@ class ListData(BaseDataElement):
             new_data[k] = new_values
         return new_data  # type:ignore
 
+    def flatten(self, item: IndexType) -> List:
+        """Flatten self[item].
+
+        Returns:
+            list: Flattened data fields.
+        """
+        return flatten_list(self[item])
+    
+    def elements_num(self, item: IndexType) -> int:
+        """int: The number of elements in self[item]."""
+        return len(self.flatten(item))
+    
+    def to_tuple(self, item: IndexType) -> tuple:
+        """tuple: The data fields in self[item] converted to tuple."""
+        return to_hashable(self[item])
+    
     def __len__(self) -> int:
         """int: The length of ListData."""
         if len(self._data_fields) > 0: