code: public BigDecimalAssert asNumber() {
          isPresent(NUMBER.getDescription());
          Node node = getNode(actual, "");
          if (node.getNodeType() == NUMBER) {
              return createBigDecimalAssert(node.decimalValue());
          } else if (node.getNodeType() == STRING) {
              try {
                  return createBigDecimalAssert(new BigDecimal(node.asText()));
              } catch (NumberFormatException e) {
                  failWithMessage("Node \"" + path + "\" can not be converted to number expected: <a number> but was: <" + quoteTextValue(node.getValue()) + ">.");
              }
          } else {
              failOnType(node, "number or string");
          }
          return null;
      }
docs: Asserts that given node is present and is of type number or a string that can be parsed as a number.