def _parse_boolean(boolean_str):
return boolean_str in ['<STR_LIT:True>', '<STR_LIT:true>', '<STR_LIT:1>']<EOL>
Attempt to parse a boolean string into a boolean value. Leniently accepts
both 'True' and 'true', but is otherwise declared false.

Args:
    boolean_str (unicode): The boolean string to parse.

Returns:
    The boolean value of the string. True if the string equals '1', 'True' or
    'true'