refactor(node.py): streamline template rendering

Removed the `_render_basic_message` function and integrated its logic directly into the `LLMNode` class. This reduces redundancy and simplifies the handling of message templates by utilizing `convert_template` more directly. This change enhances code readability and maintainability.

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

@@ -36,7 +36,6 @@ from core.variables import (
     FileSegment,
     NoneSegment,
     ObjectSegment,
-    SegmentGroup,
     StringSegment,
 )
 from core.workflow.constants import SYSTEM_VARIABLE_NODE_ID
@@ -878,11 +877,11 @@ class LLMNode(BaseNode[LLMNodeData]):
                 prompt_messages.append(prompt_message)
             else:
                 # Get segment group from basic message
-                segment_group = _render_basic_message(
-                    template=message.text,
-                    context=context,
-                    variable_pool=self.graph_runtime_state.variable_pool,
-                )
+                if context:
+                    template = message.text.replace("{#context#}", context)
+                else:
+                    template = message.text
+                segment_group = self.graph_runtime_state.variable_pool.convert_template(template)
 
                 # Process segments for images
                 file_contents = []
@@ -926,11 +925,11 @@ class LLMNode(BaseNode[LLMNodeData]):
                 variable_pool=self.graph_runtime_state.variable_pool,
             )
         else:
-            result_text = _render_basic_message(
-                template=template.text,
-                context=context,
-                variable_pool=self.graph_runtime_state.variable_pool,
-            ).text
+            if context:
+                template = template.text.replace("{#context#}", context)
+            else:
+                template = template.text
+            result_text = self.graph_runtime_state.variable_pool.convert_template(template).text
         prompt_message = _combine_text_message_with_role(text=result_text, role=PromptMessageRole.USER)
         prompt_messages.append(prompt_message)
         return prompt_messages
@@ -967,18 +966,3 @@ def _render_jinja2_message(
     )
     result_text = code_execute_resp["result"]
     return result_text
-
-
-def _render_basic_message(
-    *,
-    template: str,
-    context: str | None,
-    variable_pool: VariablePool,
-) -> SegmentGroup:
-    if not template:
-        return SegmentGroup(value=[])
-
-    if context:
-        template = template.replace("{#context#}", context)
-
-    return variable_pool.convert_template(template)