Convert LLM Attribution result to a proper dataclass (#1572)

Summary:
Pull Request resolved: #1572

Converts LLM attribution result to a proper dataclass.

Reviewed By: aobo-y

Differential Revision: D75727427

fbshipit-source-id: df983f47ed9c6a74516a1cf630ab8ef4276f0feb

Author: craymichael

captum/attr/_core/llm_attr.py

@@ -3,11 +3,9 @@
 import warnings
 
 from abc import ABC
-
 from copy import copy
-
+from dataclasses import dataclass
 from textwrap import shorten
-
 from typing import Any, Callable, cast, Dict, List, Optional, Tuple, Type, Union
 
 import matplotlib.colors as mcolors
@@ -45,24 +43,18 @@
 }
 
 
+@dataclass
 class LLMAttributionResult:
     """
     Data class for the return result of LLMAttribution,
     which includes the necessary properties of the attribution.
     It also provides utilities to help present and plot the result in different forms.
     """
 
-    def __init__(
-        self,
-        seq_attr: Tensor,
-        token_attr: Optional[Tensor],
-        input_tokens: List[str],
-        output_tokens: List[str],
-    ) -> None:
-        self.seq_attr = seq_attr
-        self.token_attr = token_attr
-        self.input_tokens = input_tokens
-        self.output_tokens = output_tokens
+    seq_attr: Tensor
+    token_attr: Optional[Tensor]
+    input_tokens: List[str]
+    output_tokens: List[str]
 
     @property
     def seq_attr_dict(self) -> Dict[str, float]: