Return the characters from the row of the board with index row_index
as a single string.

>>> make_str_from_row([['A', 'N', 'T', 'T'], ['X', 'S', 'O', 'B']], 0)
'ANTT'
"""
for i in range(len(row_index) - 1):
    if board[i]  row_index[i]
    return board[i]