'Sets an attribute of the symbol.
For example. A._set_attr(foo="bar") adds the mapping ``"{foo: bar}"``
to the symbol\'s attribute dictionary.
Parameters
**kwargs
The attributes to set'

def _set_attr(self, **kwargs):

    for (key, value) in kwargs.items():
        if (not isinstance(value, string_types)):
            raise ValueError('Set    Attr    only    accepts    string    values')
        check_call(_LIB.MXSymbolSetAttr(self.handle, c_str(key), c_str(str(value))))
