public Double getDouble(String key)  {
        Object o = getMap().get(key);
        if(o instanceof Number) {
            return ((Number)o).doubleValue();
        } else if(o == null) {
            return null;
        } else {
            return Double.parseDouble(o.toString());
        }
    }
Helper function to get a Double annotation.
<p>
This function first checks if the Object in a map is a <code>Number</code>, and then calls doubleValue() on it
If it is not, then  Double.parseDouble() is called on the string representation of the object. If the string
is not parseable as a double, a NumberFormatException is thrown.
container-search/src/main/java/com/yahoo/text/interpretation/Annotations.java