bug: Differences between OpenAi and Gemini

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Python version (python --version)

3.10.15

Operating system/version

MacOs 14.6.1

NeMo-Guardrails version (if you must use a specific version and not the latest

No response

Describe the bug

Hi, thank you for you work.
I noticed that i obtain different results with the response generator ("..." in Colang v2) when i use different providers.
If I use OpenAi, I obtain the desired response, while if i use Gemini, I receive a syntax error. Simply by changing ONLY the config file.
I am testing this using two different nemo servers: action and non action one. But they work fine and locally I have the same problem.
For the config files, i used the following ones:

colang_version: 2.x
models:
  - type: main
    engine: vertexai
    model: gemini-1.5-pro

colang_version: 2.x
models:
  - type: main
    engine: openai
    model: gpt-3.5-turbo-instruct

Using prints and logs as debug, I noticed that the error is in the line $output = ..."'{$ref_use}'"
I have tried also variation of way to send the input (for instance: $ref_use.transcript), but they did not work.
This is the error with gemini:

# This is the current conversation between the user and the bot:                                                                                                                                           
user action: user said "Hi! Can you do the spelling of the following name <PERSON>? Thanks"                                                                                                                
                                                                                                                                                                                                           
# 'Hi! Can you do the spelling of the following name <PERSON>? Thanks'                                                                                                                                     
$output =                                                                                                                                                                                                  

/Users/vrige/Library/Caches/pypoetry/virtualenvs/llm-gateway-C7tEgGBA-py3.10/lib/python3.10/site-packages/proto/message.py:389: DeprecationWarning: The argument `including_default_value_fields` has been removed from
                Protobuf 5.x. Please use `always_print_fields_with_no_presence` instead.
                
  warnings.warn(

LLM Completion (d9093..)
user intent: user asked for spelling of a name                                                                                                                                                             

17:47:27.685 | Output Stats None
17:47:27.685 | LLM call took 2.36 seconds
WARNING:nemoguardrails.actions.action_dispatcher:Error while execution 'GenerateValueAction' with parameters '{'var_name': 'output', 'instructions': "'Hi! Can you do the spelling of the following name <PERSON>? Thanks'"}': Invalid LLM response: `user intent: user asked for spelling of a name`
ERROR:nemoguardrails.actions.action_dispatcher:Invalid LLM response: `user intent: user asked for spelling of a name`
Traceback (most recent call last):
  File "/Users/vrige/Library/Caches/pypoetry/virtualenvs/llm-gateway-C7tEgGBA-py3.10/lib/python3.10/site-packages/nemoguardrails/actions/v2_x/generation.py", line 813, in generate_value
    return literal_eval(value)
  File "/Users/vrige/.pyenv/versions/3.10.15/lib/python3.10/ast.py", line 64, in literal_eval
    node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
  File "/Users/vrige/.pyenv/versions/3.10.15/lib/python3.10/ast.py", line 50, in parse
    return compile(source, filename, mode, flags,
  File "<unknown>", line 1
    user intent: user asked for spelling of a name
         ^^^^^^
SyntaxError: invalid syntax

The input message is the following one:
'Hi! Can you do the spelling of the following name <PERSON>? Thanks'

Finally, the simpleAction makes a custom validation of the output, but it works fine.

I need to work with Gemini, is there a way to overcome this problem?

Steps To Reproduce

import core
import llm

flow main
    user said something as $ref_use
    $output = ..."'{$ref_use}'"
    await analyse_output(ref_use=$output) as $ref_act_out

flow analyse_output $ref_use
    $result = await simpleAction(inputs=$ref_use)
    if "Error: " in $result
        bot say "I do not like it. Change your input"
    else
        bot say $result

UPDATE: I tried also the following simplified flow, but I got the same error.

import core
import llm

flow main
    user said something as $ref_use
    $output = ..."'{$ref_use}'"

Expected Behavior

The OpenAi response is the following one:
Sure, the spelling of the name << PERSON >> is <US_ITIN>. Is there anything else I can assist you with?

Actual Behavior

This is the error with gemini:

# This is the current conversation between the user and the bot:                                                                                                                                           
user action: user said "Hi! Can you do the spelling of the following name <PERSON>? Thanks"                                                                                                                
                                                                                                                                                                                                           
# 'Hi! Can you do the spelling of the following name <PERSON>? Thanks'                                                                                                                                     
$output =                                                                                                                                                                                                  

/Users/vrige/Library/Caches/pypoetry/virtualenvs/llm-gateway-C7tEgGBA-py3.10/lib/python3.10/site-packages/proto/message.py:389: DeprecationWarning: The argument `including_default_value_fields` has been removed from
                Protobuf 5.x. Please use `always_print_fields_with_no_presence` instead.
                
  warnings.warn(

LLM Completion (d9093..)
user intent: user asked for spelling of a name                                                                                                                                                             

17:47:27.685 | Output Stats None
17:47:27.685 | LLM call took 2.36 seconds
WARNING:nemoguardrails.actions.action_dispatcher:Error while execution 'GenerateValueAction' with parameters '{'var_name': 'output', 'instructions': "'Hi! Can you do the spelling of the following name <PERSON>? Thanks'"}': Invalid LLM response: `user intent: user asked for spelling of a name`
ERROR:nemoguardrails.actions.action_dispatcher:Invalid LLM response: `user intent: user asked for spelling of a name`
Traceback (most recent call last):
  File "/Users/vrige/Library/Caches/pypoetry/virtualenvs/llm-gateway-C7tEgGBA-py3.10/lib/python3.10/site-packages/nemoguardrails/actions/v2_x/generation.py", line 813, in generate_value
    return literal_eval(value)
  File "/Users/vrige/.pyenv/versions/3.10.15/lib/python3.10/ast.py", line 64, in literal_eval
    node_or_string = parse(node_or_string.lstrip(" \t"), mode='eval')
  File "/Users/vrige/.pyenv/versions/3.10.15/lib/python3.10/ast.py", line 50, in parse
    return compile(source, filename, mode, flags,
  File "<unknown>", line 1
    user intent: user asked for spelling of a name
         ^^^^^^
SyntaxError: invalid syntax