code: def distinct_values(t_old, t_new):   
      
      res = []
      res.append([' -- NOT IN check -- '])
      for new_col in t_new.header:
          dist_new = t_new.get_distinct_values_from_cols([new_col])
          #print('NEW Distinct values for ' + new_col + ' = ' + str(dist_new))
          for old_col in t_old.header:
              if old_col == new_col:
                  dist_old = t_old.get_distinct_values_from_cols([old_col])
                  #print('OLD Distinct values for ' + old_col + ' = ' + str(dist_old))
                  
                  # Now compare the old and new values to see what is different
                  not_in_new = [x for x in dist_old[0] if x not in dist_new[0]]
                  if not_in_new != []:
                      #print(old_col + ' not_in_new = ' , not_in_new)
                      res.append(['Not in New', old_col, not_in_new])
                      
                  not_in_old = [x for x in dist_new[0] if x not in dist_old[0]]
                  if not_in_old != []:
                      #print(new_col + ' not_in_old = ' , not_in_old)
                      res.append(['Not in Old', new_col, not_in_old])
                      
                      
      
      return sorted(res)
docs: for all columns, check which values are not in 
      the other table