code: def set_environment(self, name, value):
          
          args = ['set-environment']
          if self._add_option:
              args += [self._add_option]
  
          args += [name, value]
  
          proc = self.cmd(*args)
  
          if proc.stderr:
              if isinstance(proc.stderr, list) and len(proc.stderr) == int(1):
                  proc.stderr = proc.stderr[0]
              raise ValueError('tmux set-environment stderr: %s' % proc.stderr)
docs: Set environment ``$ tmux set-environment <name> <value>``.
  
          Parameters
          ----------
          name : str
              the environment variable name. such as 'PATH'.
          option : str
              environment value.