Bracket balance checker in Python
Looks pretty good.

A couple comments:

Unless this is an assignment to make or use a Stack, a Python list would suffice.

The code checks if a char is in '[{(', then checks if it is in ']})' and the stack is empty, then checks if it is in ']})' (again) and checks if the top of the stack is the matching bracket. All characters go through all those checks.

In general, it is good to make the common case fast and less cases can be slower.

def check_balance(code):
    """Return True if brackets are balanced, False otherwise.
    """

    valid = {']': '[', ')': '(', '}': '{'}

    lefts = []

    for char in code:
        # common case
        if char not in '[](){}':
            continue

        if char in '[({':
            lefts.append(char)

        elif not lefts or lefts.pop() != valid[char]:
            return False

    return lefts == []