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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 _get_imports_h(self, data_types):
 """Emits all necessary header file imports for the given Stone data type."""

        if not isinstance(data_types, list):
            data_types = [data_types]

        import_classes = []

        for data_type in data_types:

            if is_user_defined_type(data_type):
                import_classes.append(fmt_class_prefix(data_type))

            for field in data_type.all_fields:
                data_type, _ = unwrap_nullable(field.data_type)

                # unpack list or map
                while is_list_type(data_type) or is_map_type(data_type):
                    data_type = (data_type.value_data_type if
                        is_map_type(data_type) else data_type.data_type)

                if is_user_defined_type(data_type):
                    import_classes.append(fmt_class_prefix(data_type))

        import_classes = list(set(import_classes))
        import_classes.sort()

        return import_classes