code: def get_ins_off(self, off):
          
          idx = 0
          for i in self.get_instructions():
              if idx == off:
                  return i
              idx += i.get_length()
          return None
docs: Get a particular instruction by using the address
  
          :param off: address of the instruction
          :type off: int
  
          :rtype: an :class:`Instruction` object