code: def _subsample_site_value(self, value, event_dim=None):
      if (
          self.dim is not None
          and event_dim is not None
          and self.subsample_size < self._full_size
      ):
          event_shape = value.shape[len(value.shape) - event_dim :]
          funsor_value = to_funsor(
              value, output=funsor.Reals[event_shape]
          )
          if self.name in funsor_value.inputs:
              return to_data(funsor_value(**{self.name: self._indices}))
      return value
  
imports: from collections import OrderedDict
  from numbers import Number
  import funsor
  from pyro.contrib.funsor.handlers.named_messenger import DimRequest, DimType, GlobalNamedMessenger, NamedMessenger
  from pyro.contrib.funsor.handlers.primitives import to_data, to_funsor
  from pyro.distributions.util import copy_docs_from
  from pyro.poutine.broadcast_messenger import BroadcastMessenger
  from pyro.poutine.indep_messenger import CondIndepStackFrame
  from pyro.poutine.messenger import Messenger
  from pyro.poutine.runtime import effectful
  from pyro.poutine.subsample_messenger import SubsampleMessenger
  from pyro.util import ignore_jit_warnings
label_desc: Use image node_id 4 for calling the SubsampleMessenger obj's underlying member method code with example usage: obj._subsample_site_value(value, event_dim) and returns: value, to_data