code: def _vars_read_by(op):
      if isinstance(op, (inst.FunctionCallOp, inst.PrimOp)):
          return op.vars_in
      if isinstance(op, inst.BranchOp):
          return op.cond_var
      return []
  
file_path: probability/tensorflow_probability/python/experimental/auto_batching/allocation_strategy.py
imports: from absl import logging
  import six
  from tensorflow_probability.python.experimental.auto_batching import instructions
  from tensorflow_probability.python.experimental.auto_batching import liveness
label_desc: Use image node_id 2 for calling a global function with example usage: _vars_read_by(op) and returns: list, op, op