code: @SuppressWarnings("squid:S1698")
      private Expression literalAtom() {
          if (tokenizer.current().isSymbol("+") && tokenizer.next().isNumber()) {
              // Parse numbers with a leading + sign like +2.02 by simply ignoring the +
              tokenizer.consume();
          }
          if (tokenizer.current().isNumber()) {
              double value = Double.parseDouble(tokenizer.consume().getContents());
              if (tokenizer.current().is(Token.TokenType.ID)) {
                  String quantifier = tokenizer.current().getContents().intern();
                  if ("n" == quantifier) {
                      value /= 1000000000d;
                      tokenizer.consume();
                  } else if ("u" == quantifier) {
                      value /= 1000000d;
                      tokenizer.consume();
                  } else if ("m" == quantifier) {
                      value /= 1000d;
                      tokenizer.consume();
                  } else if ("K" == quantifier || "k" == quantifier) {
                      value *= 1000d;
                      tokenizer.consume();
                  } else if ("M" == quantifier) {
                      value *= 1000000d;
                      tokenizer.consume();
                  } else if ("G" == quantifier) {
                      value *= 1000000000d;
                      tokenizer.consume();
                  } else {
                      Token token = tokenizer.consume();
                      errors.add(ParseError.error(token,
                                                  String.format("Unexpected token: '%s'. Expected a valid quantifier.",
                                                                token.getSource())));
                  }
              }
              return new Constant(value);
          }
          Token token = tokenizer.consume();
          errors.add(ParseError.error(token,
                                      String.format("Unexpected token: '%s'. Expected an expression.",
                                                    token.getSource())));
          return Constant.EMPTY;
      }
docs: Parser rule for parsing a literal atom.
  <p>
  An literal atom is a numeric constant.
  
  @return an atom parsed from the given input