def METHOD_NAME(account_name: Account):
    """Return the type of this account's name.
    Warning: No check is made on the validity of the account type. This merely
    returns the root account of the corresponding account name.
    Args:
      account_name: A string, the name of the account whose type is to return.
    Returns:
      A string, the type of the account in 'account_name'.
    """
    assert isinstance(account_name, str), "Account is not a string: {}".format(account_name)
    return account.split(account_name)[0]