def get_current_period(root_arr: list):
    """
    Iterates through all xml-root objects in given list and returns the highest period incremented by 1 (since uploading the result of period `x` indicates that user wants to simulate period `x+1`).
    Parameters
    -----------
    `root_arr`: list
        List of xml root objects that is retrieved by `parse_all_xml()` method.
    """
    if(len(root_arr) == 0):
        return 1
    periods = []
    for root in root_arr:
        periods.append(int(root.get('period'))+1)
    return max(periods)