code: def col_transform(self, col, digits):
          
  
          if col is None or float(col) < 0.0:
              return None
          else:
              col = self.number_to_base(int(col), self.base, digits)
              if len(col) == digits:
                  return col
              else:
                  return [0 for _ in range(digits - len(col))] + col
docs: The lambda body to transform the column values