undefined is not a function (near '..._react2.default.createClass...') Why am i getting this error ?

[ZunairaMarwat]

import React , {Component} from 'react';
import { AppRegistry,Text, View, StyleSheet, Alert } from 'react-native';
import RadioForm, {RadioButton, RadioButtonInput, RadioButtonLabel} from 'react-native-simple-radio-button';

var radio_props = [
{label: 'param1', value: 0 },
{label: 'param2', value: 1 }
];

var App = React.createClass({
getInitialState: function() {
return {
value: 0,
}
},

select_function: function(value){
console.log(value);
if (value == 0) {
Alert.alert(
'Your text',
"Select param1"
);
}

if (value == 1){
Alert.alert(
'Your Text',
"Select param2"
);
}
},
render: function() {
return (

<RadioForm
radio_props={radio_props}
initial={0}
onPress={(value) => {this.setState({value:value}); this.select_function(value)}}
/>

);
}
});

AppRegistry.registerComponent('App' , () => App);