Support for guided decoding for offline LLM (#6878)

Co-authored-by: Cyrus Leung <cyrus.tl.leung@gmail.com>

vllm/model_executor/guided_decoding/guided_fields.py

@@ -0,0 +1,38 @@
+from dataclasses import dataclass
+from typing import Dict, List, Optional, TypedDict, Union
+
+from pydantic import BaseModel
+
+
+class LLMGuidedOptions(TypedDict, total=False):
+    guided_json: Union[Dict, BaseModel, str]
+    guided_regex: str
+    guided_choice: List[str]
+    guided_grammar: str
+    guided_decoding_backend: str
+    guided_whitespace_pattern: str
+    guided_json_object: bool
+
+
+@dataclass
+class GuidedDecodingRequest:
+    """One of the fields will be used to retrieve the logit processor."""
+    guided_json: Optional[Union[Dict, BaseModel, str]] = None
+    guided_regex: Optional[str] = None
+    guided_choice: Optional[List[str]] = None
+    guided_grammar: Optional[str] = None
+    guided_decoding_backend: Optional[str] = None
+    guided_whitespace_pattern: Optional[str] = None
+    guided_json_object: Optional[bool] = None
+
+    def __post_init__(self):
+        """Validate that some fields are mutually exclusive."""
+        guide_count = sum([
+            self.guided_json is not None, self.guided_regex is not None,
+            self.guided_choice is not None, self.guided_grammar is not None,
+            self.guided_json_object is not None
+        ])
+        if guide_count > 1:
+            raise ValueError(
+                "You can only use one kind of guided decoding but multiple are "
+                f"specified: {self.__dict__}")