
    Write a function that validates whether a transaction identifier follows the bank's security protocol by checking if it consists solely of lowercase letters joined with underscores. The function should return true for valid transaction identifiers that match this pattern and false for any identifiers that deviate from it.
    

    
import re

def text_lowercase_underscore(text):
    """
    Write a function that validates whether a transaction identifier follows the bank's security protocol by checking if it consists solely of lowercase letters joined with underscores. The function should return true for valid transaction identifiers that match this pattern and false for any identifiers that deviate from it.
    

    """
import re

def text_lowercase_underscore(text):
    """
    Write a function that validates whether a transaction identifier follows the bank's security protocol by checking if it consists solely of lowercase letters joined with underscores. The function should return true for valid transaction identifiers that match this pattern and false for any identifiers that deviate from it.
    

    """
    patterns = '^[a-z]+_[a-z]+$'
    if re.search(patterns, text):
        return True
    else:
        return False