def _load_gui_setting(self, key, d=None):
<EOL>pop_value = False<EOL>if d == None: <EOL><INDENT>d = self._lazy_load<EOL>pop_value = True<EOL><DEDENT>if not type(d) == dict: d = d.headers<EOL>if key in d:<EOL><INDENT>try:<EOL><INDENT>eval(key).set_value(d[key])<EOL>if pop_value: d.pop(key)<EOL><DEDENT>except: <EOL><INDENT>print("<STR_LIT>"+repr(key))<EOL><DEDENT><DEDENT>
Safely reads the header setting and sets the appropriate control
value. 

Parameters
----------
key
    Key string of the format 'self.controlname'.
d = None
    Databox instance or dictionary, presumably containing the aforementioned
    key. If d=None, pops the value from self._lazy_load.