docs: def floor_func(self, addr):
          """
          Return the function who has the greatest address that is less than or equal to `addr`.
  
          :param int addr: The address to query.
          :return:         A Function instance, or None if there is no other function before `addr`.
          :rtype:          Function or None
          """
  
          try:
              prev_addr = self._function_map.floor_addr(addr)
              return self._function_map[prev_addr]
  
          except KeyError:
              return None