code: def render_koji(self):
          
          phase = 'prebuild_plugins'
          plugin = 'koji'
          if not self.dj.dock_json_has_plugin_conf(phase, plugin):
              return
  
          if self.spec.yum_repourls.value:
              logger.info("removing koji from request "
                          "because there is yum repo specified")
              self.dj.remove_plugin(phase, plugin)
          elif not (self.spec.koji_target.value and
                    self.spec.kojiroot.value and
                    self.spec.kojihub.value):
              logger.info("removing koji from request as not specified")
              self.dj.remove_plugin(phase, plugin)
          else:
              self.dj.dock_json_set_arg(phase, plugin,
                                        "target", self.spec.koji_target.value)
              self.dj.dock_json_set_arg(phase, plugin,
                                        "root", self.spec.kojiroot.value)
              self.dj.dock_json_set_arg(phase, plugin,
                                        "hub", self.spec.kojihub.value)
              if self.spec.proxy.value:
                  self.dj.dock_json_set_arg(phase, plugin,
                                            "proxy", self.spec.proxy.value)
docs: if there is yum repo specified, don't pick stuff from koji