input: Write a python function to extract package names from the install_requires list in the provided setup script.
  assert extract_packages('''install_requires=[
          'opencensus >= 0.8.dev0, < 1.0.0',
          'wrapt >= 1.0.0, < 2.0.0',
      ]''') == ['opencensus', 'wrapt']
  assert extract_packages('''install_requires=[
          'numpy >= 1.18.0',
          'pandas >= 1.0.0, < 2.0.0',
      ]''') == ['numpy', 'pandas']
  assert extract_packages('''install_requires=[
          'requests',
      ]''') == ['requests']
output: def extract_packages(setup_script):
      import re
      pattern = r'install_requires=\[(.*?)\]'
      match = re.search(pattern, setup_script, re.DOTALL)
      if match:
          packages_str = match.group(1)
          packages = re.findall(r"'([^']+)'", packages_str)
          package_names = [pkg.split()[0] for pkg in packages]
          return package_names
      return []