Community: Fix DuckDuckGo search tool Output Format

[AndrewEffendi]

Issue: : #22961
Description:

Previously, the documentation for DuckDuckGoSearchResults said that it returns a JSON string, however the code returns a regular string that can't be parsed as is.
for example running

from langchain_community.tools import DuckDuckGoSearchResults

# Create a DuckDuckGo search instance
search = DuckDuckGoSearchResults()

# Invoke the search
result = search.invoke("Obama")

# Print the result
print(result)
# Print the type of the result
print("Result Type:", type(result))

will return

snippet: Harris will hold a campaign event with former President Barack Obama in Georgia next Thursday, the first time the pair has campaigned side by side, a senior campaign official said. A week from ..., title: Obamas to hit the campaign trail in first joint appearances with Harris, link: https://www.nbcnews.com/politics/2024-election/obamas-hit-campaign-trail-first-joint-appearances-harris-rcna176034, snippet: Item 1 of 3 Former U.S. first lady Michelle Obama and her husband, former U.S. President Barack Obama, stand on stage during Day 2 of the Democratic National Convention (DNC) in Chicago, Illinois ..., title: Obamas set to hit campaign trail with Kamala Harris for first time, link: https://www.reuters.com/world/us/obamas-set-hit-campaign-trail-with-kamala-harris-first-time-2024-10-18/, snippet: Barack and Michelle Obama will make their first campaign appearances alongside Kamala Harris at rallies in Georgia and Michigan. By Reid J. Epstein Reporting from Ashwaubenon, Wis. Here come the ..., title: Harris Will Join Michelle Obama and Barack Obama on Campaign Trail, link: https://www.nytimes.com/2024/10/18/us/politics/kamala-harris-michelle-obama-barack-obama.html, snippet: Obama's leaving office was "a turning point," Mirsky said. "That was the last time anybody felt normal." A few feet over, a 64-year-old physics professor named Eric Swanson who had grown ..., title: Obama's reemergence on the campaign trail for Harris comes as he ..., link: https://www.cnn.com/2024/10/13/politics/obama-campaign-trail-harris-biden/index.html
Result Type: <class 'str'>

After the change in this PR, DuckDuckGoSearchResults takes an additional output_format = "list" | "json" | "string" ("string" = current behavior, default). For example, invoking DuckDuckGoSearchResults(output_format="list") return a list of dictionaries in the format

[{'snippet': '...', 'title': '...', 'link': '...'}, ...]

e.g.

[{'snippet': "Obama has in a sense been wrestling with Trump's impact since the real estate magnate broke onto the political stage in 2015. Trump's victory the next year, defeating Obama's secretary of ...", 'title': "Obama's fears about Trump drive his stepped-up campaigning", 'link': 'https://www.washingtonpost.com/politics/2024/10/18/obama-trump-anxiety-harris-campaign/'}, {'snippet': 'Harris will hold a campaign event with former President Barack Obama in Georgia next Thursday, the first time the pair has campaigned side by side, a senior campaign official said. A week from ...', 'title': 'Obamas to hit the campaign trail in first joint appearances with Harris', 'link': 'https://www.nbcnews.com/politics/2024-election/obamas-hit-campaign-trail-first-joint-appearances-harris-rcna176034'}, {'snippet': 'Item 1 of 3 Former U.S. first lady Michelle Obama and her husband, former U.S. President Barack Obama, stand on stage during Day 2 of the Democratic National Convention (DNC) in Chicago, Illinois ...', 'title': 'Obamas set to hit campaign trail with Kamala Harris for first time', 'link': 'https://www.reuters.com/world/us/obamas-set-hit-campaign-trail-with-kamala-harris-first-time-2024-10-18/'}, {'snippet': 'Barack and Michelle Obama will make their first campaign appearances alongside Kamala Harris at rallies in Georgia and Michigan. By Reid J. Epstein Reporting from Ashwaubenon, Wis. Here come the ...', 'title': 'Harris Will Join Michelle Obama and Barack Obama on Campaign Trail', 'link': 'https://www.nytimes.com/2024/10/18/us/politics/kamala-harris-michelle-obama-barack-obama.html'}]
Result Type: <class 'list'>

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Name	Status	Preview	Comments	Updated (UTC)
langchain	✅ Ready (Inspect)	Visit Preview	💬 Add feedback	Oct 22, 2024 9:02pm

[vbarda]

@AndrewEffendi thank you for the contribution! i updated the change to make it backwards compatible. The behavior you introduced is still available, it just requires specifying output_format="list". let me know if you have any comments / concerns!

[AndrewEffendi]

@AndrewEffendi thank you for the contribution! i updated the change to make it backwards compatible. The behavior you introduced is still available, it just requires specifying output_format="list". let me know if you have any comments / concerns!

Looks good, thanks!