def symetry(m):
    """
    Symetrisize the values of the matrix on the y axis.
    """
    matrix = []
    for row_index in range(len(m)):
        result_row = []

        for value_index in range(len(m[0])):
            # symerization of matrix1 only by the row_index value (y axis)
            new_value = (float(m[row_index][value_index]) +
                         float(m[-row_index - 1][value_index])) / 2
            result_row.append(new_value)

        matrix.append(result_row)

    return matrix