def Validate(self, value, key):
    if isinstance(value, self.ParsedMethod):
      return value
    else:
      return self.ParsedMethod(value, key)
Validates that the string compiles as a Python callable.
dataset/ETHPy150Open AppScale/appscale/AppServer/google/appengine/ext/bulkload/bulkloader_parser.py/EvaluatedCallable.Validate