Return 'numeric' if the column is of type integer or
        real, otherwise return 'string'.

def _get_column_type(self,column):
        """ Return 'numeric' if the column is of type integer or
        real, otherwise return 'string'. """
        ctype = column.GetType()
        if ctype in [ogr.OFTInteger, ogr.OFTReal]:
            return 'numeric'
        else:
            return 'string'