import json
from datetime import datetime

def process_data(data):
    result = []
    for item in data:
        if item.get('value', 0) > 0:
            result.append({
                'id': item.get('id'),
                'processed': True,
                'timestamp': datetime.now().isoformat()
            })
    return result

def calculate_avg(nums):
    total = 0
    count = len(nums)
    for n in nums:
        total += n
    return total / count if count > 0 else 0

def filter_users(users, min_age=18):
    filtered = []
    for user in users:
        if user.get('age', 0) >= min_age:
            filtered.append(user)
    return filtered

def save_to_file(data, filename):
    with open(filename, 'w') as f:
        json.dump(data, f)
    return True

class DataStore:
    def __init__(self):
        self._data = {}

    def add(self, key, value):
        self._data[key] = value

    def get(self, key):
        return self._data.get(key)

    def remove(self, key):
        if key in self._data:
            del self._data[key]

def format_output(items):
    output = []
    for i, item in enumerate(items):
        output.append(f"{i+1}. {item}")
    return "\n".join(output)