code: public Double getDoubleAttribute(String name, Double defaultValue) {
          return getValue(doubleAttributes, name, defaultValue);
      }
docs: Gets the double value of an attribute.
  @param name The name of the attribute.  Not null.
  @param defaultValue The default value for the attribute.  May be null.  This value will be returned if this
  metadata object does not contain a double value for the specified attribute name.
  @return Either the double value of the attribute with the specified name, or the value specified by the defaultValue
  object if this metadata object does not contain a double value for the specified attribute name.
  @throws NullPointerException if name is null.