def load_currency(self, mnemonic: str):
<EOL>if self.rate and self.rate.currency == mnemonic:<EOL><INDENT>return<EOL><DEDENT>app = PriceDbApplication()<EOL>symbol = SecuritySymbol("<STR_LIT>", mnemonic)<EOL>self.rate = app.get_latest_price(symbol)<EOL>if not self.rate:<EOL><INDENT>raise ValueError(f"<STR_LIT>")<EOL><DEDENT>
load the latest rate for the given mnemonic; expressed in the base currency