class_docstr: Context manager that temporarily sets the `TZ` variable (for use on
  *nix-like systems). Because the effect is local to the shell anyway, this
  will apply *unless* a guard is set.
  
  If you do not want the TZ environment variable set, you may set the
  ``DATEUTIL_MAY_NOT_CHANGE_TZ_VAR`` variable to a truthy value.
class_docstr_tok: ["Context","manager","that","temporarily","sets","the","`","TZ","`","variable","(","for","use","on","*","nix-like","systems",")",".","Because","the","effect","is","local","to","the","shell","anyway",",","this","will","apply","*","unless","*","a","guard","is","set",".","If","you","do","not","want","the","TZ","environment","variable","set",",","you","may","set","the","``","DATEUTIL_MAY_NOT_CHANGE_TZ_VAR","``","variable","to","a","truthy","value","."]
code: def set_current_tz(self, tzval):
      if tzval is UnsetTz and "TZ" in os.environ:
          del os.environ["TZ"]
      else:
          os.environ["TZ"] = tzval
  
      time.tzset()
  
imports: from __future__ import unicode_literals
  import os
  import time
  import subprocess
  import warnings
  import tempfile
  import pickle
  import pytest
label_desc: Use image node_id 2 for calling the TZEnvContext obj's underlying member method code with example usage: obj.set_current_tz(tzval) without return types