text: import logging
  from tkp.accessors import CasaImage
  from casacore.tables import table as casacore_table
  
  logger = logging.getLogger(__name__)
  
  
  class AartfaacCasaImage(CasaImage):
  
      def __init__(self, url, plane=0, beam=None):
          super(AartfaacCasaImage, self).__init__(url, plane=0, beam=None)
          table = casacore_table(self.url.encode(), ack=False)
          self.taustart_ts = self.parse_taustartts(table)
          self.telescope = table.getkeyword('coords')['telescope']
  
          # TODO: header does't contain integration time
          # aartfaac imaginig pipeline issue #25
          self.tau_time = 1
  
      def parse_frequency(self, table):
          """
          Extract frequency related information from headers
  
          (Overrides the implementation in CasaImage, which pulls the entries
          from the 'spectral2' sub-table.)
  
          """
          keywords = table.getkeywords()
  
          # due to some undocumented casacore feature, the 'spectral' keyword
          # changes from spectral1 to spectral2 when AARTFAAC imaging developers
          # changed some of the header information. For now we will try both
          # locations.
          if 'spectral1' in keywords['coords']:
              keyword = 'spectral1'
  
          if 'spectral2' in keywords['coords']:
              keyword = 'spectral2'
  
          freq_eff = keywords['coords'][keyword]['restfreq']
          freq_bw = keywords['coords'][keyword]['wcs']['cdelt']
          return freq_eff, freq_bw
  