
    Write a function to validate customer usernames in the financial planning portal by checking if they contain only lowercase letters connected by underscores. The function should return true if the username follows this required format, and false if it contains any other characters or patterns.
    

    
import re

def text_lowercase_underscore(text):
    """
    Write a function to validate customer usernames in the financial planning portal by checking if they contain only lowercase letters connected by underscores. The function should return true if the username follows this required format, and false if it contains any other characters or patterns.
    

    """
import re

def text_lowercase_underscore(text):
    """
    Write a function to validate customer usernames in the financial planning portal by checking if they contain only lowercase letters connected by underscores. The function should return true if the username follows this required format, and false if it contains any other characters or patterns.
    

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