code: def build_mount_env(source, mounts):
    
    return '\n'.join([
        'export {0}={1}/{2}'.format(var.name, source.rstrip('/'),
                                    var.docker_path.rstrip('/')) for var in mounts
    ])
docs: Return a multi-line string with export statements for the variables.
  
    Arguments:
      source: Folder with the data. For example /mnt/data
      mounts: a list of MountParam
  
    Returns:
      a multi-line string with a shell script that sets environment variables
      corresponding to the mounts.