readonly & __Field? schemaFieldForOperation = createSchemaFieldFromOperation(self.schema.types, operationNode, self.errors, self.nodeModifierContext);

public isolated function visitField(parser:FieldNode fieldNode, anydata data = ()) {
    readonly & __Field parentField = <readonly & __Field>data;
    readonly & __Type parentType = getOfType(parentField.'type);
    readonly & __Field? requiredFieldValue = getRequiredFieldFromType(parentType, self.schema.types, fieldNode);
    readonly & __InputValue[] inputValues = requiredFieldValue is __Field ? requiredFieldValue.args : [];
    self.validateDirectiveVariables(fieldNode);
    foreach parser:ArgumentNode argument in fieldNode.getArguments() {
        argument.accept(self, inputValues);
    }
    if fieldNode.getSelections().length() > 0 {
        parser:SelectionNode[] selections = fieldNode.getSelections();
        foreach parser:SelectionNode subSelection in selections {
            subSelection.accept(self, data);
        }
    }
}