docs: automatically add api ref links (#20755)

![Screenshot 2024-04-22 at 1 51 13
PM](https://github.com/langchain-ai/langchain/assets/22008038/b8b09fec-3800-4b97-bd26-5571b8308f4a)

docs/scripts/generate_api_reference_links.py

@@ -16,7 +16,7 @@ _BASE_URL = "https://api.python.langchain.com/en/latest/"
 code_block_re = re.compile(r"^(```python\n)(.*?)(```\n)", re.DOTALL | re.MULTILINE)
 # Regular expression to match langchain import lines
 _IMPORT_RE = re.compile(
-    r"from\s+(langchain\.\w+(\.\w+)*?)\s+import\s+"
+    r"from\s+(langchain(?:_\w+)?\.\w+(?:\.\w+)*?)\s+import\s+"
     r"((?:\w+(?:,\s*)?)*"  # Match zero or more words separated by a comma+optional ws
     r"(?:\s*\(.*?\))?)",  # Match optional parentheses block
     re.DOTALL,  # Match newlines as well
@@ -70,7 +70,9 @@ def main():
         if file_imports:
             # Use relative file path as key
             relative_path = (
-                os.path.relpath(file, _DOCS_DIR).replace(".mdx", "").replace(".md", "")
+                os.path.relpath(file, args.docs_dir)
+                .replace(".mdx", "/")
+                .replace(".md", "/")
             )
 
             doc_url = f"https://python.langchain.com/docs/{relative_path}"
@@ -122,8 +124,10 @@ def replace_imports(file):
         imports = []
         for import_match in _IMPORT_RE.finditer(code):
             module = import_match.group(1)
+            if "pydantic_v1" in module:
+                continue
             imports_str = (
-                import_match.group(3).replace("(\n", "").replace("\n)", "")
+                import_match.group(2).replace("(\n", "").replace("\n)", "")
             )  # Handle newlines within parentheses
             # remove any newline and spaces, then split by comma
             imported_classes = [
@@ -140,7 +144,8 @@ def replace_imports(file):
                 except ImportError as e:
                     logger.warning(f"Failed to load for class {class_name}, {e}")
                     continue
-
+                if len(module_path.split(".")) < 2:
+                    continue
                 url = (
                     _BASE_URL
                     + module_path.split(".")[1]