code: def istrue(self):
      try:
          return self._istrue()
      except TEST_OUTCOME:
          self.exc = sys.exc_info()
          if isinstance(self.exc[1], SyntaxError):
              msg = [" " * (self.exc[1].offset + 4) + "^"]
              msg.append("SyntaxError: invalid syntax")
          else:
              msg = traceback.format_exception_only(*self.exc[:2])
          fail(
              "Error evaluating %r expression\n"
              "    %s\n"
              "%s" % (self._mark_name, self.expr, "\n".join(msg)),
              pytrace=False,
          )
  
imports: import os
  import platform
  import sys
  import traceback
  import six
  from ..outcomes import fail
  from ..outcomes import TEST_OUTCOME
label_desc: Use image node_id 6 for calling the MarkEvaluator obj's underlying member method code with example usage: obj.istrue() and returns: self