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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_types_removed_from_unions( old_schema: GraphQLSchema, new_schema: GraphQLSchema ) -> List[BreakingChange]: """Find types removed from unions. Given two schemas, returns a list containing descriptions of any breaking changes in the new_schema related to removing types from a union type. """

    old_type_map = old_schema.type_map
    new_type_map = new_schema.type_map

    types_removed_from_union = []
    for old_type_name, old_type in old_type_map.items():
        new_type = new_type_map.get(old_type_name)
        if not (is_union_type(old_type) and is_union_type(new_type)):
            continue
        old_type = cast(GraphQLUnionType, old_type)
        new_type = cast(GraphQLUnionType, new_type)
        type_names_in_new_union = {type_.name for type_ in new_type.types}
        for type_ in old_type.types:
            type_name = type_.name
            if type_name not in type_names_in_new_union:
                types_removed_from_union.append(
                    BreakingChange(
                        BreakingChangeType.TYPE_REMOVED_FROM_UNION,
                        f"{type_name} was removed from union type {old_type_name}.",
                    )
                )
    return types_removed_from_union