code: def create_package(self, doc, name):
          
          if not self.package_set:
              self.package_set = True
              doc.package = package.Package(name=name)
              return True
          else:
              raise CardinalityError('Package::Name')
docs: Creates a package for the SPDX Document.
          name - any string.
          Raises CardinalityError if package already defined.