I assume, we are talking about ObjectScript? Then you got in the main method a <SYNTAX> error because "calling" is not a command keyword. So what are you really doing? We don't need the whole main method, the line with the call would be enough. By the way, a method name like "this_method" is not a valid name except if you place it in (double)quotes.  Something, which is formal correct, looks like this:

Method "this_MainMethod"()
{
    do ..SecondMethod()
}

Method SecondMethod()
{
    // ...
}

After I put all the solutions in a pot, salting them with some own ideas then filtering, I got a really nice solution with 55 bytes. Works for all the examples given by @Eduard.Lebedyuk.

The best idea-donors where, among others, @Stuart Strickland and @Lorenzo Scalese, thank you.

ClassMethod IsValid(s)
{
	f{s c=$a(s_0,$i(i))+1 ret:$i(z,c=42-(c=41))>0!'c 'z}
}

I hope, this change does not affect the way I use (some of the) mnemonics - am I right?

Class My.Mnemonics Extends %RegisteredObject
{
/// Set-/Reset mnemonic routine
ClassMethod SetMnemonics(rou={$zname}) [ ProcedureBlock = 0 ]
{
    set old=##class(%Device).GetMnemonicRoutine()
    use $i::"^"_rou
    quit old
    
MA(x)	write "This is MA "_x quit
MB()	write "This is MB" quit
}
}


// for example:
set old=##class(My.Mnemonics).SetMnemonics()
write /ma(123)
do ##class(MyMnemonics).SetMnemonics(old)

OK, I start with 47 chars... unfortunately, I have to add 20 chars more for that (stupid) extra requirement of ignoring characters like {, [, <, etc. therefore end up with 67 chars

ClassMethod IsHalfValid(x)
{
1	s z=x,x=$replace(x,"()","") g 1:x'=z q x=""
}

ClassMethod IsFullValid(x)
{
1	s z=x,x=$replace($zstrip(x,"*e",,"()"),"()","") g 1:x'=z q x=""
}

Speed was'n asked...

In the mean time the answer is already given by Mr Maslennikov and others, but to shorten your runtime,  you could also try a "variablenless" loop, maybe this gives you some seconds more... The emphasis is on "maybe".

// if you have null-subscripts enabled
if $d(^YYY(""))!1 for i=0:1 {quit:$order(@$zr)=""} write i

// if null-subscripts are not enabled
if $d(^YYY(-9E18))!1 for i=0:1 {quit:$order(@$zr)=""} write i

// of course, you can do that on any arbitrary level too
if $d(^YYY(1,2,3,""))!1 for i=0:1 {...} write i

// the value of -9E19 ist just for explanation, use a value suitable for your needs

May I ask for the background, why do you need that node count? 

Do you have a code snippet for us? Something like

write mylist.%IsA("%ListOfDataTypes") --> 1
set item = mylist.%GetAt(2)
//
// Now the big question: what do you (want to) do with this item?
//
// do you try to lock a global: lock ^myGlobal(item) ?
// do you try to open (a possible locked) Object: set obj=##class(some.class).%OpenId(item [,4]) ?
// something else?

Somehow I don't understand your problem. If I create a simple class with a %Text property, insert some text data and then query for the word "time" I get it without problem.

Class DC.TextData Extends %Persistent
{
Property Comment As %Text(LANGUAGECLASS = "%Text.English", MAXLEN = 1000);
}

Now some data and the query

USER>d ##class(DC.TextData).%KillExtentData()

USER>s tt=##class(DC.TextData).%New(),tt.Comment="Notice, time is money." w tt.%Save()
1
USER>s tt=##class(DC.TextData).%New(),tt.Comment="It's time for a break." w tt.%Save()
1
USER>s tt=##class(DC.TextData).%New(),tt.Comment="There is no business like show business." w tt.%Save()
1
USER>d $system.SQL.Shell()
SQL Command Line Shell
----------------------------------------------------

The command prefix is currently set to: <<nothing>>.
Enter <command>, 'q' to quit, '?' for help.
[SQL]USER>>select $zversion
5.      select $zversion

Expression_1
IRIS for UNIX (Ubuntu Server LTS for x86-64) 2021.2 (Build 649U) Thu Jan 20 2022 08:49:51 EST

1 Rows(s) Affected
statement prepare time(s)/globals/cmds/disk: 0.0006s/4/140/0ms
          execute time(s)/globals/cmds/disk: 0.0008s/0/394/0ms
                          cached query class: %sqlcq.USER.cls7
---------------------------------------------------------------------------
[SQL]USER>>select * from DC.TextData where Comment %CONTAINS('time')
6.      select * from DC.TextData where Comment %CONTAINS('time')

ID      Comment
1       Notice, time is money.
2       It's time for a break.

2 Rows(s) Affected
statement prepare time(s)/globals/cmds/disk: 0.0005s/4/140/0ms
          execute time(s)/globals/cmds/disk: 0.0043s/30/4,322/0ms
                          cached query class: %sqlcq.USER.cls2
---------------------------------------------------------------------------
[SQL]USER>>quit

USER>

There are no reserved words for %Contains but there is a requirement on the field (property) type. Excuse me for my arrogance, but instead of reading the documentation everybody thinks, it's cheaper to ask a question in the developer community, to get a ready made solution. So please read this first and if something is not clear, then tell it us what you do not understand and we will help you to understand.

Maybe there are tools to dump a dynamic object, I don't know, but you can always write your own short method

/// obj: a dynamic object
/// opt: an option, how to display array elements
///      0: just show the index number
///      1: show the parenthesized index
///      2: show index number in a %Get() method
/// tag: optional, the name of the <obj> variable
/// 
ClassMethod DumpJSON(obj, opt = 2, tag = "")
{
	set itr=obj.%GetIterator(), arr=obj.%IsA("%DynamicArray") set:tag]"" tag=tag_"."
	while itr.%GetNext(.key, .val) {
		set:arr key=$case(opt, 2:"%Get("_key_")", 1:"("_key_")", :key)
		if $isobject(val), val.%IsA("%DynamicAbstractObject") {
			do ..DumpJSON(val,opt,tag_key)
		} else { write tag,key,": ",val,! }
	}
}

For ease of use, put it into the %ZLANGC00.mac, for example

%ZLANGC00   ; Command extensions

// Dump a dymanmic object
ZDDUMP(obj,opt,tag) Public { do ##class(your.utility).DumpJSON(obj,.opt,.tag) }

For the data, you mentioned above, the following will be displayed

set metaDynObj={"versionId":"2","security":[{"system":"http://terminol....}

zddump metaDynObj::"metaDynObj"
metaDynObj.versionId: 2
metaDynObj.security.%Get(0).system: http://terminology.hl7.org/CodeSystem/v3-Confidentiality
metaDynObj.security.%Get(0).code: U
metaDynObj.security.%Get(0).display: unrestricted

zddump [11,22,33]
0: 11
1: 22
2: 33

zddump [11,22,33]:1:"x"
x.(0): 11
x.(1): 22
x.(2): 33

For routines (*.int and *.mac)
- first, this is ABSOLUTE necessary, EXPORT your routines (to an file, to source-control-system, etc)
  for example: do $system.OBJ.Export(...)
- compile the routinies (which will be already done)
- delete the *.int and *.mac routinies keeping the *.obj

For classes (*.cls)
- first, this is ABSOLUTE necessary, EXPORT your classes (to an file, to source-control-system, etc)
  for example: do $system.OBJ.Export(...) do $system.OBJ.ExportPackage(...)
- compile the class(es) (which will be already done)
- put the class in deployed mode
  do $system.OBJ.MakeClassDeployed(...)
  
That's all. But DO NOT forget for the export, in elsecase you have to start over with your routines and classes by zero!