get(key, prop, functionContext) {
    const def = this.getDefinition(key, ['type', prop], functionContext);

    if (!def) return undefined;

    if (schemaDefinitionOptions.includes(prop)) {
      return def[prop];
    }

    return (def.type.find((props) => props[prop]) || {})[prop];
  }
Gets a field's property

@param {String} key The schema key, specific or generic.
@param {String} prop Name of the property to get for that schema key
@param {Object} [functionContext] The `this` context to use if prop is a function
@returns {any} The property value