code: def test_rpcs_attribute_none_if_no_rpcs(tmpdir):
      tiffname = str(tmpdir.join("test.tif"))
      with rasterio.open(
          tiffname,
          "w",
          driver="GTiff",
          dtype="uint8",
          count=1,
          width=10,
          height=10,
      ):
          pass
      with rasterio.open(tiffname) as src:
          assert src.rpcs is None
  
file_path: rasterio/tests/test_rpcs.py
imports: import rasterio
  from rasterio.rpc import RPC
label_desc: Use image node_id 6 for calling a global function with example usage: test_rpcs_attribute_none_if_no_rpcs(tmpdir) without return types