old_contents: """
  PlasmaPy is a community-developed and community-driven open source core
  Python package for plasma physics.
  """
  
  # Check that PlasmaPy is being imported from a recent enough version of
  # Python so that otherwise an appropriate ImportError with a useful
  # error message will be raised.  This check should be done before
  # anything else to avoid error messages that obfuscate the source of the
  # problem.  This file must be Python 2 compliant enough to avoid raising
  # any SyntaxError exceptions, and thus cannot have f-strings.
  
  import sys
  
  if sys.version_info < (3, 6):
      raise ImportError(
          "PlasmaPy requires Python version 3.6 or higher, but is being "
          "called from Python version {}.".format(sys.version.split()[0]))
  
  # Place all imports that require Python 3.6+ **after** the Python
  # version check.
  
  from . import import_helpers  # noqa
  
  import_helpers.check_versions()
  
  __name__ = "plasmapy"
  
  __doc__ = ("A community-developed and community-driven open source "
             "core Python package for plasma physics.")
  
  # The file version.py is created by installing PlasmaPy with setup.py
  # using functionality from astropy_helpers.  If this has not been run,
  # then we can set the default values to None.
  
  try:
      from .version import version as __version__
      from .version import githash as _githash
  except (ImportError, ModuleNotFoundError):  # coveralls: ignore
      __version__ = None
      _githash = None
  
  try:
      from . import atomic
      from . import classes
      from . import constants
      from . import diagnostics
      from . import mathematics
      from . import physics
      from . import utils
  except ImportError:
      raise ImportError("Unable to load PlasmaPy subpackages.")
  
  # Clean up the top-level namespace
  
  del sys, import_helpers
  
new_contents: """
  PlasmaPy is a community-developed and community-driven open source core
  Python package for plasma physics.
  """
  
  # Check that PlasmaPy is being imported from a recent enough version of
  # Python so that otherwise an appropriate ImportError with a useful
  # error message will be raised.  This check should be done before
  # anything else to avoid error messages that obfuscate the source of the
  # problem.  This file must be Python 2 compliant enough to avoid raising
  # any SyntaxError exceptions, and thus cannot have f-strings.
  
  import sys
  
  if sys.version_info < (3, 6):
      raise ImportError(
          "PlasmaPy requires Python version 3.6 or higher, but is being "
          "called from Python version {}.".format(sys.version.split()[0]))
  
  # Place all imports that require Python 3.6+ **after** the Python
  # version check.
  
  from . import import_helpers  # noqa
  
  import_helpers.check_versions()
  
  # The dunder namespace should be reserved for the special objects that
  # are specified in Python documentation (e.g., __name__, __doc__, and
  # __version__).  All hidden objects that are specific to PlasmaPy
  # should start with a single underscore (e.g., _githash).
  
  __name__ = "plasmapy"
  
  __doc__ = ("A community-developed and community-driven open source "
             "core Python package for plasma physics.")
  
  # The file version.py is created by installing PlasmaPy with setup.py
  # using functionality from astropy_helpers.  If this has not been run,
  # then set the default values to None.
  
  try:
      from .version import version as __version__
      from .version import githash as _githash
  except (ImportError, ModuleNotFoundError):
      __version__ = None
      _githash = None
  
  try:
      from . import atomic
      from . import classes
      from . import constants
      from . import diagnostics
      from . import mathematics
      from . import physics
      from . import utils
  except (ImportError, ModuleNotFoundError) as exc:
      raise ImportError("Unable to load PlasmaPy subpackages.") from exc
  
  # Clean up the top-level namespace.
  
  del sys, import_helpers
  
subject: Update main __init__.py