
    Write a function that validates whether a bank transaction code contains a risk indicator pattern consisting of a credit event flag ('a') immediately followed by either two or three verification markers ('b'), which is crucial for accurate credit score calculation.
    

    
import re

def text_match_two_three(text):
    """
    Write a function that validates whether a bank transaction code contains a risk indicator pattern consisting of a credit event flag ('a') immediately followed by either two or three verification markers ('b'), which is crucial for accurate credit score calculation.
    

    """
import re

def text_match_two_three(text):
    """
    Write a function that validates whether a bank transaction code contains a risk indicator pattern consisting of a credit event flag ('a') immediately followed by either two or three verification markers ('b'), which is crucial for accurate credit score calculation.
    

    """
    patterns = 'ab{2,3}'
    if re.search(patterns, text):
        return True
    else:
        return False