code: def build_srcdict(gta, prop):
      
      o = {}
      for s in gta.roi.sources:
          o[s.name] = s[prop]
      return o
docs: Build a dictionary that maps from source name to the value of a source property
  
      Parameters
      ----------
  
      gta : `fermipy.GTAnalysis`
          The analysis object
  
      prop : str
          The name of the property we are mapping
  
  
      Returns
      -------
  
      odict : dict
          Dictionary that maps from source name to the value of the specified property