code: def FetchSizeOfSignedBinary(binary_urn,
                              token = None
                             ):
    
    if _ShouldUseLegacyDatastore():
      try:
        aff4_stream = aff4.FACTORY.Open(
            binary_urn, aff4_type=collects.GRRSignedBlob, mode="r", token=token)
        return aff4_stream.size
      except aff4.InstantiationError:
        raise SignedBinaryNotFoundError(binary_urn)
    else:
      try:
        references, _ = data_store.REL_DB.ReadSignedBinaryReferences(
            _SignedBinaryIDFromURN(binary_urn))
      except db.UnknownSignedBinaryError:
        raise SignedBinaryNotFoundError(binary_urn)
      last_reference = references.items[-1]
      return last_reference.offset + last_reference.size
docs: Returns the size of the given binary (in bytes).
  
    Args:
      binary_urn: RDFURN that uniquely identifies the binary.
      token: ACL token to use with the legacy (non-relational) datastore.
  
    Raises:
      SignedBinaryNotFoundError: If no signed binary with the given URN exists.