code: def extract_refs_by_indices(exprs, indices):
      """Returns a set of references in `exprs` with indices `indices`.
  
      Parameters
      ----------
      expr : Expression
      indices : Indices
  
      Returns
      -------
      Set[str]
      """
      s = set()
      for e in exprs:
          for name, inds in get_refs(e).items():
              if inds == indices:
                  s.add(name)
      return s
  
file_path: hail/hail/python/hail/expr/expressions/expression_utils.py
imports: from typing import Set, Dict
  from hail.typecheck import typecheck, setof
  from .indices import Indices, Aggregation
  from ..expressions import Expression, ExpressionException, expr_any
  from ...ir import MakeTuple
label_desc: Use image node_id 6 for calling a global function with example usage: extract_refs_by_indices(exprs, indices) and returns: s