code: def get_src_names(gta):
      
      o = []
      for s in gta.roi.sources:
          o += [s.name]
      return sorted(o)
docs: Build and return a list of source name
  
      Parameters
      ----------
  
      gta : `fermipy.GTAnalysis`
          The analysis object
  
  
      Returns
      -------
  
      l : list
         Names of the source