list method
Lists all columns for a report type
Request parameters:
reportType - Report type. Allowed Values: 'ga'. Where 'ga' corresponds
to the Core Reporting API
Value must have pattern ga.
$fields - Selector specifying which fields to include in a partial
response.
Completes with a Columns.
Completes with a commons.ApiRequestError if the API endpoint returned an error.
If the used http.Client completes with an error when making a REST call,
this method will complete with the same error.
Implementation
async.Future<Columns> list(
  core.String reportType, {
  core.String? $fields,
}) async {
  final queryParams_ = <core.String, core.List<core.String>>{
    if ($fields != null) 'fields': [$fields],
  };
  final url_ =
      'metadata/' + commons.escapeVariable('$reportType') + '/columns';
  final response_ = await _requester.request(
    url_,
    'GET',
    queryParams: queryParams_,
  );
  return Columns.fromJson(response_ as core.Map<core.String, core.dynamic>);
}