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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def read_config(ini_group=None):
 """ Read the configuration from the environment, or config. First it try to go for the environment, then it overrides those with the cloudstack.ini file. """

    env_conf = dict(DEFAULT_CONFIG)
    for key in REQUIRED_CONFIG_KEYS.union(ALLOWED_CONFIG_KEYS):
        env_key = "CLOUDSTACK_{0}".format(key.upper())
        value = os.getenv(env_key)
        if value:
            env_conf[key] = value

    # overrides means we have a .ini to read
    overrides = os.getenv('CLOUDSTACK_OVERRIDES', '').strip()

    if not overrides and set(env_conf).issuperset(REQUIRED_CONFIG_KEYS):
        return env_conf

    ini_conf = read_config_from_ini(ini_group)

    overrides = {s.lower() for s in re.split(r'\W+', overrides)}
    config = dict(dict(env_conf, **ini_conf),
                  **{k: v for k, v in env_conf.items() if k in overrides})

    missings = REQUIRED_CONFIG_KEYS.difference(config)
    if missings:
        raise ValueError("the configuration is missing the following keys: " +
                         ", ".join(missings))

    # convert booleans values.
    bool_keys = ('dangerous_no_tls_verify',)
    for bool_key in bool_keys:
        if isinstance(config[bool_key], string_type):
            try:
                config[bool_key] = strtobool(config[bool_key])
            except ValueError:
                pass

    return config