code: def addColumn(self, col, index=None):
          'Insert column at given index or after all columns.'
          if col:
              if index is None:
                  index = len(self.columns)
              col.sheet = self
              self.columns.insert(index, col)
              return cof addColumn(self, col, index=None):
          'Insert column at given index or after all columns.'
          if col:
              if index is None:
                  index = len(self.columns)
              col.sheet = self
              self.columns.insert(index, col)
              return col
docs: Insert column at given index or after all columns.