old_contents: import sys
  import importlib
  from distutils.version import LooseVersion
  
  
  def check_python(minimum_python_version):
      """Raises an ImportError if the version of Python is not at least
      the version given by a string representing the minimum version
      number."""
  
      required_python = LooseVersion(minimum_python_version)
      current_python = LooseVersion(sys.version)
  
      if current_python < required_python:
          raise ImportError(f"PlasmaPy requires Python {minimum_python_version} "
                            "or newer.") from None
  
  
  def check_versions(minimum_versions):
      """Raises an ImportError if a dependent package is not installed
      and at the required version number, or provides a warning if the
      version of the dependent package cannot be found."""
  
      for module_name in minimum_versions.keys():
          minimum_version = LooseVersion(minimum_versions[module_name])
  
          try:
              module = importlib.import_module(module_name)
              module_version = LooseVersion(module.__version__)
          except ImportError:
              raise ImportError(f"Unable to import {module_name} while "
                                "importing PlasmaPy.") from None
          except AttributeError:
              warnings.warn(f"{module_name} version {minimum_version.vstring} "
                            "is required for PlasmaPy.  However, the version of "
                            f"{module_name} could not be determined to check if "
                            "this requirement is met.")
          else:
              if minimum_version > module_version:
                  raise ImportError(
                      f"{module_name} {minimum_version} or newer is required "
                      "for PlasmaPy. The currently installed version is "
                      f"{module_version}.") from None
  
new_contents: import sys
  import importlib
  import warnings
  from distutils.version import LooseVersion
  
  
  def check_python(minimum_python_version):
      """Raises an ImportError if the version of Python is not at least
      the version given by a string representing the minimum version
      number."""
  
      required_python = LooseVersion(minimum_python_version)
      current_python = LooseVersion(sys.version)
  
      if current_python < required_python:
          raise ImportError(f"PlasmaPy requires Python {minimum_python_version} "
                            "or newer.") from None
  
  
  def check_versions(minimum_versions):
      """Raises an ImportError if a dependent package is not installed
      and at the required version number, or provides a warning if the
      version of the dependent package cannot be found."""
  
      for module_name in minimum_versions.keys():
          minimum_version = LooseVersion(minimum_versions[module_name])
  
          try:
              module = importlib.import_module(module_name)
              module_version = LooseVersion(module.__version__)
          except ImportError:
              raise ImportError(f"Unable to import {module_name} while "
                                "importing PlasmaPy.") from None
          except AttributeError:
              warnings.warn(f"{module_name} version {minimum_version.vstring} "
                            "is required for PlasmaPy.  However, the version of "
                            f"{module_name} could not be determined to check if "
                            "this requirement is met.")
          else:
              if minimum_version > module_version:
                  raise ImportError(
                      f"{module_name} {minimum_version} or newer is required "
                      "for PlasmaPy. The currently installed version is "
                      f"{module_version}.") from None
  
subject: Add missing import statement in import_helpers.py