class_docstr: This class allows to capture writes to FD1 and FD2
  and may connect a NULL file to FD0 (and prevent
  reads from sys.stdin).  If any of the 0,1,2 file descriptors
  is invalid it will not be captured.
code: def _save(self):
      in_ = self._options["in_"]
      out = self._options["out"]
      err = self._options["err"]
      mixed = self._options["mixed"]
      patchsys = self._options["patchsys"]
      if in_:
          try:
              self.in_ = FDCapture(
                  0, tmpfile=None, now=False, patchsys=patchsys
              )
          except OSError:
              pass
      if out:
          tmpfile = None
          if hasattr(out, "write"):
              tmpfile = out
          try:
              self.out = FDCapture(
                  1, tmpfile=tmpfile, now=False, patchsys=patchsys
              )
              self._options["out"] = self.out.tmpfile
          except OSError:
              pass
      if err:
          if out and mixed:
              tmpfile = self.out.tmpfile
          elif hasattr(err, "write"):
              tmpfile = err
          else:
              tmpfile = None
          try:
              self.err = FDCapture(
                  2, tmpfile=tmpfile, now=False, patchsys=patchsys
              )
              self._options["err"] = self.err.tmpfile
          except OSError:
              pass
  
imports: import os
  import sys
  import py
  import tempfile
label_desc: Use image node_id 2 for calling the StdCaptureFD obj's underlying member method code with example usage: obj._save() without return types