code: def set_file_license_comment(self, doc, text):
          
          if self.has_package(doc) and self.has_file(doc):
              if not self.file_license_comment_set:
                  self.file_license_comment_set = True
                  self.file(doc).license_comment = text
                  return True
              else:
                  raise CardinalityError('File::LicenseComment')
          else:
              raise OrderError('File::LicenseComment')
docs: Raises OrderError if no package or file defined.
          Raises CardinalityError if more than one per file.