code: def prev(self, n=1):
          
          # Current position - #data
          i = abs(self.tell - n)
  
          # Get the next n data starting from i
          return self.get(i, n)
docs: Get the previous n data from file.
  
          Keyword argument:
              n -- number of structs to be retrieved (default 1)
                   Must be greater than 0.
  
          Return:
              A data in the format of obj_fmt, if n = 1. A list of
              structs, otherwise.