feat: use latest duckduckgo_search API to call (langchain-ai#6409)

# Provider the latest duckduckgo_search API

The Git commit contents involve two files related to some DuckDuckGo
query operations, and an upgrade of the DuckDuckGo module to version
3.8.3. A suitable commit message could be "Upgrade DuckDuckGo module to
version 3.8.3, including query operations". Specifically, in the
duckduckgo_search.py file, a DDGS() class instance is newly added to
replace the previous ddg() function, and the time parameter name in the
get_snippets() and results() methods is changed from "time" to
"timelimit" to accommodate recent changes. In the pyproject.toml file,
the duckduckgo-search module is upgraded to version 3.8.3.

[duckduckgo_search readme
attention](https://github.com/deedy5/duckduckgo_search): Versions before
v2.9.4 no longer work as of May 12, 2023

## Who can review?

@vowelparrot

---------

Co-authored-by: Harrison Chase <hw.chase.17@gmail.com>

langchain/utilities/duckduckgo_search.py

@@ -40,19 +40,23 @@ def validate_environment(cls, values: Dict) -> Dict:
 
     def get_snippets(self, query: str) -> List[str]:
         """Run query through DuckDuckGo and return concatenated results."""
-        from duckduckgo_search import ddg
-
-        results = ddg(
-            query,
-            region=self.region,
-            safesearch=self.safesearch,
-            time=self.time,
-            max_results=self.max_results,
-        )
-        if results is None or len(results) == 0:
-            return ["No good DuckDuckGo Search Result was found"]
-        snippets = [result["body"] for result in results]
-        return snippets
+        from duckduckgo_search import DDGS
+
+        with DDGS() as ddgs:
+            results = ddgs.text(
+                query,
+                region=self.region,
+                safesearch=self.safesearch,
+                timelimit=self.time,
+            )
+            if results is None or next(results, None) is None:
+                return ["No good DuckDuckGo Search Result was found"]
+            snippets = []
+            for i, res in enumerate(results, 1):
+                snippets.append(res["body"])
+                if i == self.max_results:
+                    break
+            return snippets
 
     def run(self, query: str) -> str:
         snippets = self.get_snippets(query)
@@ -71,24 +75,28 @@ def results(self, query: str, num_results: int) -> List[Dict[str, str]]:
                 title - The title of the result.
                 link - The link to the result.
         """
-        from duckduckgo_search import ddg
-
-        results = ddg(
-            query,
-            region=self.region,
-            safesearch=self.safesearch,
-            time=self.time,
-            max_results=num_results,
-        )
-
-        if results is None or len(results) == 0:
-            return [{"Result": "No good DuckDuckGo Search Result was found"}]
-
-        def to_metadata(result: Dict) -> Dict[str, str]:
-            return {
-                "snippet": result["body"],
-                "title": result["title"],
-                "link": result["href"],
-            }
-
-        return [to_metadata(result) for result in results]
+        from duckduckgo_search import DDGS
+
+        with DDGS() as ddgs:
+            results = ddgs.text(
+                query,
+                region=self.region,
+                safesearch=self.safesearch,
+                timelimit=self.time,
+            )
+            if results is None or next(results, None) is None:
+                return [{"Result": "No good DuckDuckGo Search Result was found"}]
+
+            def to_metadata(result: Dict) -> Dict[str, str]:
+                return {
+                    "snippet": result["body"],
+                    "title": result["title"],
+                    "link": result["href"],
+                }
+
+            formatted_results = []
+            for i, res in enumerate(results, 1):
+                formatted_results.append(to_metadata(res))
+                if i == num_results:
+                    break
+            return formatted_results