chore(api/core): Improve FileVar's type hint and imports. (#7290)

api/core/workflow/nodes/llm/llm_node.py

@@ -1,14 +1,13 @@
 import json
 from collections.abc import Generator
 from copy import deepcopy
-from typing import Optional, cast
+from typing import TYPE_CHECKING, Optional, cast
 
 from core.app.entities.app_invoke_entities import ModelConfigWithCredentialsEntity
 from core.app.entities.queue_entities import QueueRetrieverResourcesEvent
 from core.entities.model_entities import ModelStatus
 from core.entities.provider_entities import QuotaUnit
 from core.errors.error import ModelCurrentlyNotSupportError, ProviderTokenNotInitError, QuotaExceededError
-from core.file.file_obj import FileVar
 from core.memory.token_buffer_memory import TokenBufferMemory
 from core.model_manager import ModelInstance, ModelManager
 from core.model_runtime.entities.llm_entities import LLMUsage
@@ -39,6 +38,10 @@ from models.model import Conversation
 from models.provider import Provider, ProviderType
 from models.workflow import WorkflowNodeExecutionStatus
 
+if TYPE_CHECKING:
+    from core.file.file_obj import FileVar
+
+
 
 class LLMNode(BaseNode):
     _node_data_cls = LLMNodeData
@@ -71,7 +74,7 @@ class LLMNode(BaseNode):
             node_inputs = {}
 
             # fetch files
-            files: list[FileVar] = self._fetch_files(node_data, variable_pool)
+            files = self._fetch_files(node_data, variable_pool)
 
             if files:
                 node_inputs['#files#'] = [file.to_dict() for file in files]
@@ -322,7 +325,7 @@ class LLMNode(BaseNode):
 
         return inputs
 
-    def _fetch_files(self, node_data: LLMNodeData, variable_pool: VariablePool) -> list[FileVar]:
+    def _fetch_files(self, node_data: LLMNodeData, variable_pool: VariablePool) -> list["FileVar"]:
         """
         Fetch files
         :param node_data: node data
@@ -521,7 +524,7 @@ class LLMNode(BaseNode):
                                query: Optional[str],
                                query_prompt_template: Optional[str],
                                inputs: dict[str, str],
-                               files: list[FileVar],
+                               files: list["FileVar"],
                                context: Optional[str],
                                memory: Optional[TokenBufferMemory],
                                model_config: ModelConfigWithCredentialsEntity) \