Cannot resolve method 'getSupportFragmentManager()'

Running this in a fragment
trying to get basic example working,

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.annotation.Nullable;
import android.support.v4.app.Fragment;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.Toast;

import com.abdeveloper.library.MultiSelectDialog;
import com.abdeveloper.library.MultiSelectModel;

import java.util.ArrayList;

public class NewChatThreadFragment extends Fragment {

    private String TAG = "Cancel";

    Button show_dialog_btn;

    MultiSelectDialog multiSelectDialog;

    @Nullable
    @Override
    public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {

        View view = inflater.inflate(R.layout.fragment_new_chat_thread, container, false);

        show_dialog_btn = view.findViewById(R.id.show_dialog);
        show_dialog_btn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                multiSelectDialog.show(getSupportFragmentManager(), "multiSelectDialog");
            }
        });

        //preselected Ids of Country List
        final ArrayList<Integer> alreadySelectedCountries = new ArrayList<>();
        alreadySelectedCountries.add(1);
        alreadySelectedCountries.add(3);
        alreadySelectedCountries.add(4);
        alreadySelectedCountries.add(7);

        //List of Countries with Name and Id
        ArrayList<MultiSelectModel> listOfCountries= new ArrayList<>();
        listOfCountries.add(new MultiSelectModel(1,"INDIA"));
        listOfCountries.add(new MultiSelectModel(2,"USA"));
        listOfCountries.add(new MultiSelectModel(3,"UK"));
        listOfCountries.add(new MultiSelectModel(4,"UAE"));
        listOfCountries.add(new MultiSelectModel(5,"JAPAN"));
        listOfCountries.add(new MultiSelectModel(6,"SINGAPORE"));
        listOfCountries.add(new MultiSelectModel(7,"CHINA"));
        listOfCountries.add(new MultiSelectModel(8,"RUSSIA"));
        listOfCountries.add(new MultiSelectModel(9,"BANGLADESH"));
        listOfCountries.add(new MultiSelectModel(10,"BELGIUM"));
        listOfCountries.add(new MultiSelectModel(11,"DENMARK"));
        listOfCountries.add(new MultiSelectModel(12,"GERMANY"));
        listOfCountries.add(new MultiSelectModel(13,"HONG KONG"));
        listOfCountries.add(new MultiSelectModel(14,"INDONESIA"));
        listOfCountries.add(new MultiSelectModel(15,"NETHERLAND"));
        listOfCountries.add(new MultiSelectModel(16,"NEW ZEALAND"));
        listOfCountries.add(new MultiSelectModel(17,"PORTUGAL"));
        listOfCountries.add(new MultiSelectModel(18,"KUWAIT"));
        listOfCountries.add(new MultiSelectModel(19,"QATAR"));
        listOfCountries.add(new MultiSelectModel(20,"SAUDI ARABIA"));
        listOfCountries.add(new MultiSelectModel(21,"SRI LANKA"));
        listOfCountries.add(new MultiSelectModel(130,"CANADA"));


        //MultiSelectModel
        multiSelectDialog = new MultiSelectDialog()
                .title("Title") //setting title for dialog
                .titleSize(25)
                .positiveText("Done")
                .negativeText("Cancel")
                .setMinSelectionLimit(0)
                .setMaxSelectionLimit(listOfCountries.size())
                .preSelectIDsList(alreadySelectedCountries) //List of ids that you need to be selected
                .multiSelectList(listOfCountries) // the multi select model list with ids and name
                .onSubmit(new MultiSelectDialog.SubmitCallbackListener() {
                    @Override
                    public void onSelected(ArrayList<Integer> selectedIds, ArrayList<String> selectedNames, String dataString) {
                        //will return list of selected IDS
                        for (int i = 0; i < selectedIds.size(); i++) {
                            Toast.makeText(getContext(), "Selected Ids : " + selectedIds.get(i) + "\n" +
                                    "Selected Names : " + selectedNames.get(i) + "\n" +
                                    "DataString : " + dataString, Toast.LENGTH_SHORT).show();
                        }


                    }

                    @Override
                    public void onCancel() {
                        Log.d(TAG,"Dialog cancelled");

                    }
                });
        return view;
    }
}

what am i missing?