code: def _exec_callers(xinst, result):
      
      for depkey, depval in xinst.dependencies.items():
          if depval.target is not None:
              if depval.target.name in result:
                  if xinst not in result[depval.target.name]:
                      result[depval.target.name].append(xinst)
              else:
                  result[depval.target.name] = [xinst]
  
      for xname, xvalue in xinst.executables:
          _exec_callers(xvalue, result)
docs: Adds the dependency calls from the specified executable instance
      to the results dictionary.