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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 generate_IR(self):
 """Parses the text of each spec and returns an API description. Returns None if an error was encountered during parsing."""


        raw_api = []
        for partial_ast in self._partial_asts:
            namespace_ast_node = self._extract_namespace_ast_node(partial_ast)
            namespace = self.api.ensure_namespace(namespace_ast_node.name)
            base_name = self._get_base_name(namespace.name, namespace.name)
            self._item_by_canonical_name[base_name] = namespace_ast_node
            if namespace_ast_node.doc is not None:
                namespace.add_doc(namespace_ast_node.doc)
            raw_api.append((namespace, partial_ast))
            self._add_data_types_and_routes_to_api(namespace, partial_ast)

        self._add_imports_to_env(raw_api)
        self._merge_patches()
        self._populate_type_attributes()
        self._populate_field_defaults()
        self._populate_enumerated_subtypes()
        self._populate_route_attributes()
        self._populate_examples()
        self._validate_doc_refs()
        self._validate_annotations()
        if self._routes is not None:
            self._filter_namespaces_by_route_whitelist()

        self.api.normalize()

        return self.api