def __init__(self, name, host='127.0.0.1', port=27017):
        self.name = name
        self.host = host
        self.port = port
def row_col(self, ind):
        i = 0
        for r in range(self.nr):
            for c in range(self.nc):
                if i == ind:
                    return r, c
                i += 1