code: async function transform({ datapath, filepath, inverse = false }) {
  	assert.string(datapath)
  	assert.string(filepath)
  	const data = await loadData(datapath)
  	const contextdoc = await loadData(filepath)
  	assert.object(data)
  	assert.object(contextdoc)
  	const result = new Context(contextdoc).use(viewPlugin).map(data)
  	return result
  }
docs: transforms data at datapath with context at filepath
  
  @param {object} props
  @param {string} props.datapath - path to data
  @param {string} [props.filepath] - path to context definition file
  @param {boolean} [props.inverse] - true for outbound (subscription) transformation
  @returns