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If I am reading this correctly, then it is NOT a dictionary: it is a nascent database creater/manager.
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What do you think a tuple/row is? Its an ordered list of values. Combine a tuple with a schema (meta data about what is in each location) and its a set of key-value pairs. Which is the same as a dictionary - a set of key value pairs.
Is that a database? Sure. What is the underlying implementation of this database? I don't know or care - could be an interface that interacts with a SQL database table or view, or it could be an in memory data structure like an array of dictionaries.
The dictionary in this instance is being used as the match qualifier ('where' statement). Again, a dictionary is just a convenient programming construct for set of key-value pairs.
I think you have a lot of conceptual issues around programming for databases.