code: def download(self, id_, packages, python, platform):
      # Unfortunately all the packages need to be catalogued in package cache
      # because of which this function can't be parallelized
  
      # Micromamba is painfully slow in determining if many packages are infact
      # already cached. As a perf heuristic, we check if the environment already
      # exists to short circuit package downloads.
      if self.path_to_environment(id_, platform):
          return
  
      prefix = "{env_dirs}/{keyword}/{platform}/{id}".format(
          env_dirs=self.info()["envs_dirs"][0],
          platform=platform,
          keyword="metaflow",  # indicates metaflow generated environment
          id=id_,
      )
  
      # Another forced perf heuristic to skip cross-platform downloads.
      if os.path.exists(f"{prefix}/fake.done"):
          return
  
      with tempfile.TemporaryDirectory() as tmp_dir:
          env = {
              "CONDA_SUBDIR": platform,
          }
          cmd = [
              "create",
              "--yes",
              "--no-deps",
              "--download-only",
              "--safety-checks=disabled",
              "--no-extra-safety-checks",
              "--repodata-ttl=86400",
              "--prefix=%s/prefix" % tmp_dir,
              "--quiet",
          ]
          for package in packages:
              cmd.append("{url}".format(**package))
  
          self._call(cmd, env)
          # Perf optimization to skip cross-platform downloads.
          if platform != self.platform():
              os.makedirs(prefix, exist_ok=True) or open(
                  f"{prefix}/fake.done", "w"
              ).close()
          return
  
imports: import json
  import os
  import subprocess
  import tempfile
  from metaflow.exception import MetaflowException
  from metaflow.util import which
  from .utils import conda_platform
label_desc: Use image node_id 3 for calling the Micromamba obj's underlying member method code with example usage: obj.download(id_, packages, python, platform) without return types