<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _parse_bold(self):
 """Parse wiki-style bold."""

        reset = self._head
        try:
            stack = self._parse(contexts.STYLE_BOLD)
        except BadRoute:
            self._head = reset
            if self._context & contexts.STYLE_SECOND_PASS:
                self._emit_text("'")
                return True
            elif self._context & contexts.STYLE_ITALICS:
                self._context |= contexts.STYLE_PASS_AGAIN
                self._emit_text("'''")
            else:
                self._emit_text("'")
                self._parse_italics()
        else:
            self._emit_style_tag("b", "'''", stack)