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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 _error(self, *args):
 """ Creates and adds one or multiple errors. :param args: Accepts different argument's signatures. *1. Bulk addition of errors:* - :term:`iterable` of :class:`~cerberus.errors.ValidationError`-instances The errors will be added to :attr:`~cerberus.Validator._errors`. *2. Custom error:* - the invalid field's name - the error message A custom error containing the message will be created and added to :attr:`~cerberus.Validator._errors`. There will however be fewer information contained in the error (no reference to the violated rule and its constraint). *3. Defined error:* - the invalid field's name - the error-reference, see :mod:`cerberus.errors` - arbitrary, supplemental information about the error A :class:`~cerberus.errors.ValidationError` instance will be created and added to :attr:`~cerberus.Validator._errors`. """

        if len(args) == 1:
            self._errors.extend(args[0])
            self._errors.sort()
            for error in args[0]:
                self.document_error_tree.add(error)
                self.schema_error_tree.add(error)
                self.error_handler.emit(error)
        elif len(args) == 2 and isinstance(args[1], _str_type):
            self._error(args[0], errors.CUSTOM, args[1])
        elif len(args) >= 2:
            field = args[0]
            code = args[1].code
            rule = args[1].rule
            info = args[2:]

            document_path = self.document_path + (field,)

            schema_path = self.schema_path
            if code != errors.UNKNOWN_FIELD.code and rule is not None:
                schema_path += (field, rule)

            if not rule:
                constraint = None
            else:
                field_definitions = self._resolve_rules_set(self.schema[field])
                if rule == 'nullable':
                    constraint = field_definitions.get(rule, False)
                elif rule == 'required':
                    constraint = field_definitions.get(rule, self.require_all)
                    if rule not in field_definitions:
                        schema_path = "__require_all__"
                else:
                    constraint = field_definitions[rule]

            value = self.document.get(field)

            self.recent_error = errors.ValidationError(
                document_path, schema_path, code, rule, constraint, value, info
            )
            self._error([self.recent_error])