Field	Type	Required	Description
blockOptions.method.args.item blockOptions.method.args.expression	item expression	+	Id of an item/expression whose value will be used as an operand for the string operation.
blockOptions.method.args.operation	string	+	Operation, which will be fulfilled. Possible values: begin, end, contain, length, not_begin, not_end, not_contain, not_length.
blockOptions.method.args.value	int/string	+	Argument of the string operation. int for length and not_length operations, string – for all other cases.