code: def _pluck_feature_pacts(pr_body: str) -> FrozenSet[str]:
      
      feature_pact_lines = [line for line in pr_body.split('\r\n')
                            if line.startswith('feature-pacts:')]
      if not feature_pact_lines:
          return frozenset()
      if len(feature_pact_lines) > 1:
          raise GithubPrError(f'There should only be one feature-pacts line. "{feature_pact_lines}"')
      return frozenset(feature_pact_lines[0].split()[1:])
docs: # Returns set with one feature pact if specified
      >>> body = 'gitlab: mygitlaburl.com\\r\\nfeature-pacts: zh-feature-a'
      >>> _pluck_feature_pacts(body) == frozenset({'zh-feature-a'})
      True
  
      # Returns set with multiple feature pacts if specified
      >>> body = 'gitlab: mygitlaburl.com\\r\\nfeature-pacts: zh-feature-a eh-feature-b\\r\\nurgent!'
      >>> _pluck_feature_pacts(body) == frozenset({'zh-feature-a', 'eh-feature-b'})
      True
  
      # Returns empty set if no feature-pacts line
      >>> body = 'gitlab: mygitlaburl.com\\r\\n\\r\\nJust adding some documentation'
      >>> _pluck_feature_pacts(body)
      frozenset()
  
      # Returns empty set if feature-pacts line with no tags
      >>> body = 'gitlab: mygitlaburl.com\\r\\n\\r\\nfeature-pacts:\\r\\nJust adding some docs'
      >>> _pluck_feature_pacts(body)
      frozenset()
  
      # Raises a GithubPrError if multiple feature-pact lines found
      >>> body = 'feature-pacts: zh-feature-a\\r\\nfeature-pacts: eh-feature-b'
      >>> _pluck_feature_pacts(body)
      Traceback (most recent call last):
          ...
      faaspact_verifier.delivery.github_prs.GithubPrError: ...