code: def pip_install_requirements() -> int:
      """
      install the requirements of the current python version.
      return 0 if success, anything else is an error.
      """
  
      extras = check_for_package_extras()
      print(
          f"""
  Installing requirements.
  
  Airflow is installed with "{extras}" extra.
  
  ----------------------------------------------------------------------------------------
  
  IMPORTANT NOTE ABOUT EXTRAS !!!
  
  You can specify extras as single coma-separated parameter to install. For example
  
  * devel - to have all development dependencies required to test core.
  * devel-* - to selectively install tools that we use to run scripts, tests, static checks etc.
  * google,amazon,microsoft_azure - to install dependencies needed at runtime by specified providers
  * devel-all-dbs - to have all development dependencies required for all DB providers
  * devel-all - to have all development dependencies required for all providers
  
  Note that "devel-all" installs all possible dependencies and we have > 600 of them,
  which might not be possible to install cleanly on your host because of lack of
  system packages. It's easier to install extras one-by-one as needed.
  
  ----------------------------------------------------------------------------------------
  
  """
      )
      version = get_python_version()
      constraint = (
          f"https://raw.githubusercontent.com/apache/airflow/constraints-main/"
          f"constraints-source-providers-{version}.txt"
      )
      pip_install_command = [
          "pip",
          "install",
          "-e",
          f".[{extras}]",
          "--constraint",
          constraint,
      ]
      quoted_command = " ".join(
          [shlex.quote(parameter) for parameter in pip_install_command]
      )
      print()
      print(f"Running command: \n   {quoted_command}\n")
      e = subprocess.run(pip_install_command)
      return e.returncode
  
file_path: airflow/scripts/tools/initialize_virtualenv.py
imports: from __future__ import annotations
  import os
  import shlex
  import shutil
  import subprocess
  import sys
  from pathlib import Path
label_desc: Use image node_id 4 for calling a global function with example usage: pip_install_requirements() and returns: e