Parse package trees and report on any discrepancies.

def main(self):
        """Parse package trees and report on any discrepancies."""
        args = self.args
        parsed_pytree, pypackages = self.parse_py_tree(pytree=args.pytree)
        parsed_doctree = self.parse_doc_tree(doctree=args.doctree, pypackages=pypackages)
        return self.compare_trees(parsed_pytree=parsed_pytree, parsed_doctree=parsed_doctree)