code: def system(session):
      
  
      # Sanity check: Only run system tests if the environment variable is set.
      if not os.environ.get('GOOGLE_APPLICATION_CREDENTIALS', ''):
          session.skip('Credentials must be set via environment variable.')
  
      # Use pre-release gRPC for system tests.
      session.install('--pre', 'grpcio')
  
      # Install all test dependencies, then install this package into the
      # virtualenv's dist-packages.
      session.install('mock', 'pytest')
      for local_dep in LOCAL_DEPS:
          session.install('-e', local_dep)
      systest_deps = [
          '../bigquery/',
          '../pubsub/',
          '../storage/',
          '../test_utils/',
      ]
      for systest_dep in systest_deps:
          session.install('-e', systest_dep)
      session.install('-e', '.')
  
      # Run py.test against the system tests.
      session.run(
          'py.test',
          '-vvv',
          '-s',
          'tests/system',
          *session.posargs)
docs: Run the system test suite.