def set_annotation(self):
        """Appends the context's ``pending_symbol`` to its ``annotations`` sequence."""
        assert self.pending_symbol is not None
        assert not self.value
        annotations = (_as_symbol(self.pending_symbol, is_symbol_value=False),)  # pending_symbol becomes an annotation
        self.annotations = annotations if not self.annotations else self.annotations + annotations
        self.ion_type = None
        self.pending_symbol = None  # reset pending symbol
        self.quoted_text = False
        self.line_comment = False
        self.is_self_delimiting = False
        return self
Appends the context's ``pending_symbol`` to its ``annotations`` sequence.