class_docstr: A PEP 302 meta path importer for finding optionally-vendored
  or otherwise naturally-installed packages from root_name.
code: def __init__(self, root_name, vendored_names=(), vendor_pkg=None):
      self.root_name = root_name
      self.vendored_names = set(vendored_names)
      self.vendor_pkg = vendor_pkg or root_name.replace(
          "extern", "_vendor"
      )
  
imports: import sys
label_desc: Use image node_id 1 to create a new VendorImporter object  with example: obj = VendorImporter(root_name, vendored_names, vendor_pkg)