Uniphore Software Systems processes structured text in conversational transcripts. Given a transcript fragment containing parentheses and bracket characters, determine whether every opening delimiter is closed with the correct type and in the correct order.
Supported delimiter pairs are (), [], and {}. All other characters, including letters, digits, spaces, and punctuation, must be ignored. An empty string is considered balanced.
Implement is_balanced(text), where text is a string. Return True if all delimiters are balanced and properly nested; otherwise, return False.
def is_balanced(text):