code: def verify_signature(self, signature_filename, data_filename,
                           keystore=None):
          
          if not self.gpg:
              raise DistlibException('verification unavailable because gpg '
                                     'unavailable')
          cmd = self.get_verify_command(signature_filename, data_filename,
                                        keystore)
          rc, stdout, stderr = self.run_command(cmd)
          if rc not in (0, 1):
              raise DistlibException('verify command failed with error '
                               'code %s' % rc)
          return rc == 0
docs: Verify a signature for a file.
  
          :param signature_filename: The pathname to the file containing the
                                     signature.
          :param data_filename: The pathname to the file containing the
                                signed data.
          :param keystore: The path to a directory which contains the keys
                           used in verification. If not specified, the
                           instance's ``gpg_home`` attribute is used instead.
          :return: True if the signature was verified, else False.