A function mapping a pyarrow DataType to a pandas `ExtensionDtype`.
                This can be used to override the default pandas type for conversion
                of built-in pyarrow types or in absence of `pandas_metadata` in the
                Table schema. The function receives a pyarrow DataType and is
                expected to return a pandas `ExtensionDtype` or `None` if the
                default conversion should be used for that type. If you have
                a dictionary mapping, you can pass `dict.get` as function.