def connect(self): 
        try:
            self.connection = pymongo.Connection(self.host, self.port)
            self.db = self.connection[self.name]
        except AutoReconnect:
            raise DatabaseException("It's not possible connect to the database")
def dec_c(self, ind):
        r, c = self.row_col(ind)
        c -= 1
        if c < 0:
            c = self.nc - 1
        if r == (self.nr - 1) and c == (self.nc - 1):
            c = self.nc - 2
        return self.indx(r, c)