code: def export(self, export_type, what):
          
          aids, arefs, spec, key = self.parse(what)
          if key.startswith('rlz'):
              curves = self.export_curves_rlzs(aids, key)
          else:  # statistical exports
              curves = self.export_curves_stats(aids, key)
          return getattr(self, 'export_' + export_type)(spec, arefs, curves)
docs: :param export_type: 'csv', 'json', ...
          :param what: string describing what to export
          :returns: list of exported file names