docs: def set_values(self, **kwargs):
          """
          Sets environment variables values.
  
          Usage::
  
              >>> environment = Environment()
              >>> environment.set_values(JOHN="DOE", DOE="JOHN")
              True
              >>> import os
              >>> os.environ["JOHN"]
              'DOE'
              >>> os.environ["DOE"]
              'JOHN'
  
          :param \*\*kwargs: Variables : Values.
          :type \*\*kwargs: \*
          :return: Method success.
          :rtype: unicode
  
          :note: Any variable with a **None** value will be skipped.
          """
  
          self.__variables.update(kwargs)
  
          for key, value in self.__variables.iteritems():
              if value is None:
                  continue
              LOGGER.debug("> Setting environment variable '{0}' with value '{1}'.".format(key, value))
              os.environ[key] = value
          return True