Add a bearer token to the request uri, body or authorization header.

def _add_bearer_token(self, uri, http_method='GET', body=None,
                          headers=None, token_placement=None):
        """Add a bearer token to the request uri, body or authorization header."""
        if token_placement == AUTH_HEADER:
            headers = tokens.prepare_bearer_headers(self.access_token, headers)

        elif token_placement == URI_QUERY:
            uri = tokens.prepare_bearer_uri(self.access_token, uri)

        elif token_placement == BODY:
            body = tokens.prepare_bearer_body(self.access_token, body)

        else:
            raise ValueError("Invalid token placement.")
        return uri, headers, body