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.
docstr: return snapshot value of stdout/stderr capturings. 
docstr_tok: ["return","snapshot","value","of","stdout\/stderr","capturings","."]
code: def readouterr(self):
      """return snapshot value of stdout/stderr capturings."""
      if hasattr(self, "out"):
          out = self._readsnapshot(self.out.tmpfile)
      else:
          out = ""
      if hasattr(self, "err"):
          err = self._readsnapshot(self.err.tmpfile)
      else:
          err = ""
      return out, err
  
imports: import os
  import sys
  import py
  import tempfile
label_desc: Use image node_id 6 for calling the StdCaptureFD obj's underlying member method code with example usage: obj.readouterr() and returns: out,  err