This module's data layout specification, as a string.

def data_layout(self):
        """
        This module's data layout specification, as a string.
        """
        # LLVMGetDataLayout() points inside a std::string managed by LLVM.
        with ffi.OutputString(owned=False) as outmsg:
            ffi.lib.LLVMPY_GetDataLayout(self, outmsg)
            return str(outmsg)