anchor.diff:  status_stmt : STATUS_KEYWORD status_arg stmtend;
   position_stmt : POSITION_KEYWORD string stmtend;
   bit_stmt : BIT_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt |position_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
  -bits_specification : (bit_stmt )+;
  -union_specification : (type_stmt )+;
  -identityref_specification : base_stmt ;
  +bits_specification : bit_stmt (bit_stmt | identifier_stmt)*;
  +union_specification : type_stmt (identifier_stmt | type_stmt )+;
  +identityref_specification : base_stmt  ;
   instance_identifier_specification : (require_instance_stmt )?;
   require_instance_arg :string; // TRUE_KEYWORD | FALSE_KEYWORD;
   require_instance_stmt : REQUIRE_INSTANCE_KEYWORD require_instance_arg stmtend;
   path_stmt : PATH_KEYWORD string stmtend;
   leafref_specification : path_stmt;
   enum_stmt : ENUM_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt |value_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
  -enum_specification : (enum_stmt )+;
  +enum_specification : enum_stmt (identifier_stmt | enum_stmt )+;
   default_stmt : DEFAULT_KEYWORD string stmtend;
   pattern_stmt : PATTERN_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt |error_message_stmt | error_app_tag_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
   length_stmt : LENGTH_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt |error_message_stmt | error_app_tag_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
   string_restrictions : (length_stmt | pattern_stmt )*;
   fraction_digits_stmt : FRACTION_DIGITS_KEYWORD string stmtend;
  -decimal64_specification : numerical_restrictions? fraction_digits_stmt | fraction_digits_stmt numerical_restrictions?;
  +decimal64_specification : (numerical_restrictions? (identifier_stmt)* fraction_digits_stmt | fraction_digits_stmt (identifier_stmt)* numerical_restrictions?);
   range_stmt : RANGE_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt |error_message_stmt | error_app_tag_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
   numerical_restrictions : range_stmt ;
  -type_body_stmts : numerical_restrictions | decimal64_specification | string_restrictions | enum_specification | leafref_specification | identityref_specification | instance_identifier_specification | bits_specification | union_specification;
  +type_body_stmts : (identifier_stmt)* (numerical_restrictions | decimal64_specification | string_restrictions | enum_specification | leafref_specification | identityref_specification | instance_identifier_specification | bits_specification | union_specification) (identifier_stmt)*;
   type_stmt : TYPE_KEYWORD string (SEMICOLON | (LEFT_BRACE  type_body_stmts RIGHT_BRACE));
  -typedef_stmt : TYPEDEF_KEYWORD string LEFT_BRACE  (type_stmt | units_stmt | default_stmt | status_stmt | description_stmt | reference_stmt )+ RIGHT_BRACE;
  +typedef_stmt : TYPEDEF_KEYWORD string LEFT_BRACE  (identifier_stmt | type_stmt | units_stmt | default_stmt | status_stmt | description_stmt | reference_stmt )+ RIGHT_BRACE;
   if_feature_stmt : IF_FEATURE_KEYWORD string stmtend;
  -feature_stmt : FEATURE_KEYWORD string (SEMICOLON | (LEFT_BRACE  (if_feature_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
  +feature_stmt : FEATURE_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt | if_feature_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
   base_stmt : BASE_KEYWORD string stmtend;
  -identity_stmt : IDENTITY_KEYWORD string (SEMICOLON | (LEFT_BRACE  (base_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
  +identity_stmt : IDENTITY_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt | base_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
   yin_element_arg : string; // TRUE_KEYWORD | FALSE_KEYWORD;
   yin_element_stmt : YIN_ELEMENT_KEYWORD yin_element_arg stmtend;
  -argument_stmt : ARGUMENT_KEYWORD string (SEMICOLON | (LEFT_BRACE  (yin_element_stmt )? RIGHT_BRACE));
  -extension_stmt : EXTENSION_KEYWORD string (SEMICOLON | (LEFT_BRACE  (argument_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
  +argument_stmt : ARGUMENT_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt)? (yin_element_stmt )? (identifier_stmt)* RIGHT_BRACE));
  +extension_stmt : EXTENSION_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt | argument_stmt | status_stmt | description_stmt | reference_stmt )* RIGHT_BRACE));
   revision_date_stmt : REVISION_DATE_KEYWORD string stmtend;
   revision_stmt : REVISION_KEYWORD string (SEMICOLON | (LEFT_BRACE  (description_stmt )? (reference_stmt )? RIGHT_BRACE));
   units_stmt : UNITS_KEYWORD string stmtend;
  
positive.code: import_stmt : IMPORT_KEYWORD string LEFT_BRACE  prefix_stmt  (revision_date_stmt )? RIGHT_BRACE;
  yang_version_stmt : YANG_VERSION_KEYWORD string stmtend;
  data_def_stmt : container_stmt | leaf_stmt | leaf_list_stmt | list_stmt | choice_stmt | anyxml_stmt | uses_stmt;
  body_stmts : ((extension_stmt | feature_stmt | identity_stmt | typedef_stmt | grouping_stmt | data_def_stmt | augment_stmt | rpc_stmt | notification_stmt | deviation_stmt) )*;
  revision_stmts : (revision_stmt )*;
  linkage_stmts : (import_stmt | include_stmt )*;
  meta_stmts : (organization_stmt | contact_stmt | description_stmt | reference_stmt )*;
  
negative.code: 
  identifier_stmt : IDENTIFIER string? stmtend;
                    
  stmtend : (SEMICOLON identifier_stmt?) | (LEFT_BRACE identifier_stmt? RIGHT_BRACE);
  deviate_replace_stmt : DEVIATE_KEYWORD string /* REPLACE_KEYWORD */ (SEMICOLON | (LEFT_BRACE (identifier_stmt |type_stmt | units_stmt | default_stmt | config_stmt | mandatory_stmt | min_elements_stmt | max_elements_stmt )* RIGHT_BRACE));
  deviate_delete_stmt : DEVIATE_KEYWORD string /* DELETE_KEYWORD */ (SEMICOLON | (LEFT_BRACE (identifier_stmt |units_stmt | must_stmt | unique_stmt | default_stmt )* RIGHT_BRACE));
  deviate_add_stmt : DEVIATE_KEYWORD string /*ADD_KEYWORD*/ (SEMICOLON | (LEFT_BRACE (identifier_stmt |units_stmt | must_stmt | unique_stmt | default_stmt | config_stmt | mandatory_stmt  | min_elements_stmt  | max_elements_stmt )* RIGHT_BRACE));
  deviate_not_supported_stmt : DEVIATE_KEYWORD string /*NOT_SUPPORTED_KEYWORD*/ (SEMICOLON | (LEFT_BRACE identifier_stmt? RIGHT_BRACE));
  deviation_stmt : DEVIATION_KEYWORD string LEFT_BRACE (identifier_stmt |description_stmt | reference_stmt | deviate_not_supported_stmt | deviate_add_stmt | deviate_replace_stmt | deviate_delete_stmt)+ RIGHT_BRACE;
  notification_stmt : NOTIFICATION_KEYWORD string (SEMICOLON | (LEFT_BRACE (identifier_stmt |if_feature_stmt | status_stmt | description_stmt | reference_stmt | typedef_stmt | grouping_stmt | data_def_stmt )* RIGHT_BRACE));
  output_stmt : OUTPUT_KEYWORD LEFT_BRACE (identifier_stmt |typedef_stmt | grouping_stmt | data_def_stmt )+ RIGHT_BRACE;
  input_stmt : INPUT_KEYWORD LEFT_BRACE (identifier_stmt |typedef_stmt | grouping_stmt | data_def_stmt )+ RIGHT_BRACE;
  rpc_stmt : RPC_KEYWORD string (SEMICOLON | (LEFT_BRACE (identifier_stmt |if_feature_stmt  | status_stmt | description_stmt | reference_stmt | typedef_stmt | grouping_stmt | input_stmt | output_stmt )* RIGHT_BRACE));
  when_stmt : WHEN_KEYWORD string (SEMICOLON | (LEFT_BRACE (identifier_stmt |description_stmt | reference_stmt )* RIGHT_BRACE));
  
  augment_stmt : AUGMENT_KEYWORD string LEFT_BRACE  (identifier_stmt |when_stmt | if_feature_stmt | status_stmt | description_stmt | reference_stmt | data_def_stmt | case_stmt)+ RIGHT_BRACE;
  uses_augment_stmt : AUGMENT_KEYWORD string LEFT_BRACE  (identifier_stmt |when_stmt | if_feature_stmt | status_stmt | description_stmt | reference_stmt | data_def_stmt | case_stmt)+ RIGHT_BRACE;
  refine_anyxml_stmts : (identifier_stmt |must_stmt | config_stmt | mandatory_stmt | description_stmt | reference_stmt )*;
  refine_case_stmts : (identifier_stmt |description_stmt | reference_stmt )*;
  refine_choice_stmts : (identifier_stmt |default_stmt | config_stmt | mandatory_stmt | description_stmt | reference_stmt )*;
  refine_list_stmts : (identifier_stmt |must_stmt | config_stmt | min_elements_stmt | max_elements_stmt | description_stmt | reference_stmt )*;
  refine_leaf_list_stmts : (identifier_stmt |must_stmt | config_stmt | min_elements_stmt | max_elements_stmt | description_stmt | reference_stmt )*;
  refine_leaf_stmts : (identifier_stmt |must_stmt | default_stmt | config_stmt | mandatory_stmt | description_stmt | reference_stmt )*;
  refine_container_stmts : (identifier_stmt |must_stmt | presence_stmt | config_stmt | description_stmt | reference_stmt )*;
  refine_pom : (refine_container_stmts | refine_leaf_stmts | refine_leaf_list_stmts | refine_list_stmts | refine_choice_stmts | refine_case_stmts | refine_anyxml_stmts);
  refine_stmt : REFINE_KEYWORD string (SEMICOLON | (LEFT_BRACE  (refine_pom) RIGHT_BRACE));
  uses_stmt : USES_KEYWORD string (SEMICOLON | (LEFT_BRACE  (identifier_stmt |when_stmt | if_feature_stmt | status_stmt | description_stmt | reference_stmt | refine_stmt | uses_augment_stmt )* RIGHT_BRACE));
  