code: def _get_picard_cmd(self, command, memscale=None):
          
          resources = config_utils.get_resources("picard", self._config)
          if memscale:
              jvm_opts = get_picard_opts(self._config, memscale=memscale)
          elif resources.get("jvm_opts"):
              jvm_opts = resources.get("jvm_opts")
          else:
              jvm_opts = self._jvm_opts
          if os.path.isdir(self._picard_ref):
              dist_file = self._get_jar(command)
              return ["java"] + jvm_opts + get_default_jvm_opts() + ["-jar", dist_file]
          else:
              # XXX Cannot currently set JVM opts with picard-tools script
              return [self._picard_ref, command]
docs: Retrieve the base Picard command, handling both shell scripts and directory of jars.