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# Built-in Types

## CPython Types

Python types like str match types like PyUnicode in the Concrete Objects Layer of CPython. They have check functions like PyUnicode_Check(), which Shiboken generates into the code checking the function arguments.

These types occur as parameters when adding functions or modifying types, as type on add-conversion within a conversion-rule or as target language API types on primitive-type.

They are built into Shiboken as custom types along with their check functions.