//Don't have to see. start------------------------------------------
var read = require('readline').createInterface({
  input: process.stdin, output: process.stdout
});
var obj; var inLine = [];
read.on('line', function(input){inLine.push(input);});
read.on('close', function(){
  obj = init(inLine);
  console.error('\n↑入力 ↓出力');
  Main();
});
function makeClone(obj){return (obj instanceof Set) ? new Set(Array.from(obj)) : JSON.parse(JSON.stringify(obj));}
function nextInt(){return myconv(next(),1);} function nextStrArray(){return myconv(next(),2);}
function nextIntArray(){return myconv(next(),4);} function nextCharArray(){return myconv(next(),6);}
function next(){return obj.next();} function hasNext(){return obj.hasNext();}
function init(input){  
  return {
    list : input, index : 0, max : input.length,
    hasNext : function(){return (this.index < this.max);},
    next : function(){if(this.hasNext()){return this.list[this.index++];}else{throw 'ArrayIndexOutOfBoundsException ‚There is no more input';}}
  };
}
function myout(s){console.log(s);}
function myerr(s){console.error('debug:' + require('util').inspect(s,false,null));}
//param "no" is
//unknown or outlier : return i. 1: parseInt.
//2: split space. 4: split space and parseInt.
//6: split 1 character. 7: split 1 character and parseInt.
//8: join space. 9: join nextline. 0: join no character.
function myconv(i,no){try{switch(no){case 1:return parseInt(i);case 2:return i.split(' ');case 4:return i.split(' ').map(Number);case 6:return i.split('');case 7:return i.split('').map(Number);case 8:return i.join(' ');case 9:return i.join('\n');case 0:return i.join('');default:return i;}}catch(e){return i;}}

//Don't have to see. end------------------------------------------
function Main(){
  var one = nextIntArray();
  var N = one[0];
  var K = one[1];
  var list = new Array(N);
  for(var i = 0; i < N; i++){
    list[i] = {
      child : [],
      no : i,
      count : 0,
      access : false
    };
  }
  for(var i = 0; i < N - 1; i++){
    var tmp = nextIntArray();
    list[tmp[0] - 1].child.push(tmp[1] - 1);
    list[tmp[1] - 1].child.push(tmp[0] - 1);
  }
  var output = 1;
  var mod = 1000000007;
  list[0].access = true;

  var stack = [[0, K, 0]];
  while(stack.length > 0){
    var tmp = stack.pop();
    var parentNodeCount = tmp[0];
    var color = tmp[1];
    var now = tmp[2];
    list[now].count = color;
    if(parentNodeCount < 2){
      parentNodeCount++;
    }
    var child = list[now].child;
    var successCount = 0;
    for(var i = 0; i < child.length; i++){
      if(!list[child[i]].access){
        list[child[i]].access = true;
        stack.push([parentNodeCount, K - successCount - parentNodeCount, child[i]]);
        successCount++;
      }
    }
  }
  for(var i = 0; i < N; i++){
    output *= list[i].count;
    output %= mod;
    if(output == -0){
      myout(0);
      return;
    }
    if(output == 0){
      break;
    }
  }
  myout(output);


  function dfs(parentNodeCount, color, now, constK){
    list[now].count = color;
    if(parentNodeCount < 2){
      parentNodeCount++;
    }
    var child = list[now].child;
    var successCount = 0;
    for(var i = 0; i < child.length; i++){
      if(!list[child[i]].access){
        list[child[i]].access = true;
        dfs(parentNodeCount, constK - successCount - parentNodeCount, child[i], constK);
        successCount++;
      }
    }
  }
}