Determining the balance of brackets in a string

It is necessary to write a function areBracketsBalanced that takes a string expr, which may contain only the characters ()[]{}. The function should return True if all brackets are opened and closed correctly, otherwise – False.

def areBracketsBalanced(expr):
    stack = []

    for char in expr:
        if char in ["(", "{", "["]:
            stack.append(char)
        else:
            if not stack:
                return False
            current_char = stack.pop()
            if current_char == "(":
                if char != ")":
                    return False
            if current_char == "{":
                if char != "}":
                    return False
            if current_char == "[":
                if char != "]":
                    return False

    return not stack