code: def AddColumn(self, column, default="", col_index=-1):
          
          if column in self.table:
              raise TableError("Column %r already in table." % column)
          if col_index == -1:
              self._table[0][column] = column
              for i in range(1, len(self._table)):
                  self._table[i][column] = default
          else:
              self._table[0].Insert(column, column, col_index)
              for i in range(1, len(self._table)):
                  self._table[i].Insert(column, default, col_index)
docs: Appends a new column to the table.
  
      Args:
        column: A string, name of the column to add.
        default: Default value for entries. Defaults to ''.
        col_index: Integer index for where to insert new column.
  
      Raises:
        TableError: Column name already exists.