accessing
fromUserName: twitterName andId: numericString
	| tweet |
	tweet := self new.
	^ Tweet storedInstances detect: [ :each | each id = numericString ] 
		ifNone: [ | tweetUrl xmlTweet |
			tweetUrl := NitterUser nitterProvider, twitterName, '/status/', numericString.
			xmlTweet := (NitterUser new documentTreeFor: tweetUrl) 
				xpath: '//div[@class="main-tweet"]'.
			^ xmlTweet
	  ].