<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def is_type_target(self):
 """Returns the CustomType instance if this executable is an embedded procedure in a custom type declaration; else False. """

        if self._is_type_target is None:
            #All we need to do is search through the custom types in the parent
            #module and see if any of their executables points to this method.
            self._is_type_target = False
            for tkey in self.module.types:
                custype = self.module.types[tkey]
                for execkey, execinst in custype.executables.items():
                    if execinst.target is self:
                        self._is_type_target = custype
                        break
                if self._is_type_target:
                    break

        return self._is_type_target