code: def get_program(self, program_path, controller=None):
          
          if not program_path or program_path[0] != '/':
              raise ValueError("program_path must be a full path with leading slash")
  
          items = program_path[1:].split('/')
          result = self
          for item in items:
              result = result[item]
  
          if hasattr(result, "lower"):
              # string redirect
              return self.get_program(result)
  
          elif type(result) is Manifest:
              return result.get_program('/')
  
          elif hasattr(result, 'append'):
              matching_blank = []
              for program in result:
                  if controller in program.controllers:
                      return program
              
                  if not program.controllers or not controller:
                      # no exact matching controllers for this program.
                      # Use the first controller with no
                      matching_blank.append(program)
              if matching_blank:
                  return matching_blank[0]
              else:
                  raise ProgramNotFound("No matcning program for %s controller" % controller)
  
          return result
docs: Find the program within this manifest. If key is found, and it contains
          a list, iterate over the list and return the program that matches
          the controller tag. NOTICE: program_path must have a leading slash.