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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def find_one(self, collection, selector={}):
 """Return one item from a collection Arguments: collection - collection to search Keyword Arguments: selector - the query (default returns first item found)"""

        for _id, doc in self.collection_data.data.get(collection, {}).items():
            doc.update({'_id': _id})
            if selector == {}:
                return doc
            for key, value in selector.items():
                if key in doc and doc[key] == value:
                    return doc
        return None