code: def _get_pip_install_mlflow():
      """
      Returns a command to pip-install mlflow. If the MLFLOW_HOME environment variable exists,
      returns "pip install -e {MLFLOW_HOME} 1>&2", otherwise
      "pip install mlflow=={mlflow.__version__} 1>&2".
      """
      mlflow_home = os.getenv("MLFLOW_HOME")
      if mlflow_home:  # dev version
          return f"pip install -e {mlflow_home} 1>&2"
      else:
          return f"pip install mlflow=={VERSION} 1>&2"
  
imports: import logging
  import os
  import re
  import subprocess
  import sys
  import tempfile
  import yaml
  from packaging.requirements import InvalidRequirement, Requirement
  from packaging.version import Version
  from mlflow.environment_variables import _MLFLOW_TESTING
  from mlflow.exceptions import MlflowException
  from mlflow.protos.databricks_pb2 import INVALID_PARAMETER_VALUE
  from mlflow.utils import PYTHON_VERSION, insecure_hash
  from mlflow.utils.process import _exec_cmd
  from mlflow.utils.requirements_utils import _infer_requirements, _parse_requirements
  from mlflow.version import VERSION
label_desc: Use image node_id 20 for calling a global function with example usage: _get_pip_install_mlflow() and returns: str, mlflow_home, str, str, VERSION, str