def extract_subelements(vector):
    """ Transform multiple element list into a 1D vector

    Function 'extract_subelements' return [1,2,3,1] from an oririginal vector
    like [[1,2,3], [1]]

    Args:
        vector (list of list): Original list of list

    Returns:
        extracted (list): Return 1D list
    """

    extracted = []
    for elem in vector:
        for value in elem :
            extracted.append(value)

    return extracted