What parameter or option in Pyan allows for the specification of the initial function when generating a callgraph?

Question

I'm using the following code to build a callgraph with Pyan. However, due to the project's size, constructing the callgraph takes a considerable amount of time. Is there a way I can specify the starting function for the callgraph?

from pyan.analyzer import CallGraphVisitor

dirname = os.path.dirname(file) filenames = glob(os.path.join(dirname, "test_code/**/*.py"), recursive=True) callgraph = CallGraphVisitor(filenames, logger=logging.getLogger(), root=dirname)