code: def _pre_action(self) -> None:
      if (
          "metrics" in self.data
          and isinstance(self.data["metrics"], list)
          and len(self.data["metrics"]) > 0
      ):
          self.data["metric"] = self.data["metrics"][0]
  
imports: from typing import Any
  from superset.utils.core import as_list
  from .base import MigrateViz
label_desc: Use image node_id 1 for calling the MigrateTreeMap obj's underlying member method code with example usage: obj._pre_action() without return types