code: def _reachable(dupe_cover: Mapping[Any, frozenset[int]]) -> int:
      return (
          len(frozenset.union(*dupe_cover.values()))
          if dupe_cover
          else 0
      )
  
file_path: dedupe/dedupe/branch_and_bound.py
imports: from __future__ import annotations
  import functools
  from typing import Any, Iterable, Mapping, Sequence, Tuple
  from ._typing import Cover
  from .predicates import Predicate
label_desc: Use image node_id 1 for calling a global function with example usage: _reachable(dupe_cover) and returns: unknown