Light GraphRAG (#4585)

### What problem does this PR solve?

#4543

### Type of change

- [x] New Feature (non-breaking change which adds functionality)

graphrag/general/mind_map_prompt.py

@@ -0,0 +1,35 @@
+#
+#  Copyright 2024 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+MIND_MAP_EXTRACTION_PROMPT = """
+- Role: You're a talent text processor to summarize a piece of text into a mind map.
+
+- Step of task:
+  1. Generate a title for user's 'TEXT'。
+  2. Classify the 'TEXT' into sections of a mind map.
+  3. If the subject matter is really complex, split them into sub-sections and sub-subsections. 
+  4. Add a shot content summary of the bottom level section.
+
+- Output requirement:
+  - Generate at least 4 levels.
+  - Always try to maximize the number of sub-sections. 
+  - In language of 'Text'
+  - MUST IN FORMAT OF MARKDOWN
+
+-TEXT-
+{input_text}
+
+"""