def find_next_group(group_str, style='()'):
    """
    Return the next group of data contained in a specified style pair from a string.
    Example:
    find_next_group('(a=1)(b=2)') returns 'a=1'

    :param group_str: Any string to search for a group.
    :param style: Start and end characters of a group. Default='()'
    :return: First group found in the group string.
    """
    cnt = 0
    for i, c in enumerate(group_str):
        if c == style[0]:
            cnt += 1
        elif c == style[1]:
            cnt -= 1
        if cnt == 0:
            return group_str[1:i]
    return None