code: def num_children(self) -> int:
      return len(self.entries) + 1 if self.entries else 0
  
imports: import abc
  import bisect
  import math
  from typing import Optional
  from .const import ENDIAN, NODE_TYPE_BYTES, USED_PAGE_LENGTH_BYTES, PAGE_REFERENCE_BYTES, TreeConf
  from .entry import Entry, Record, Reference, OpaqueData
label_desc: Use image node_id 2 for calling the ReferenceNode obj's underlying member method code with example usage: obj.num_children() and returns: unknown