Imports a (potentially large) CSV file with API actions to be executed. The file will be imported asynchronously as a job. Use getMultiResults to get the job status. This method requires your development API clientKey. See CSV uploads for more on using multi to upload user attributes, events, and device attributes.
The file should contain a header row with the API argument names that are found in the API documentation, such as userId, deviceId, and action (if defaultAction is not specified). To indicate nested JSON arguments, use a dot within the column name, such as userAttributes.Gender.