function d3_selection(groups) {

  d3_arraySubclass(groups, d3_selectionPrototype);

  return groups;

}

var d3_select = function(s, n) { return n.querySelector(s); },

    d3_selectAll = function(s, n) { return n.querySelectorAll(s); };

// Prefer Sizzle, if available.

if (typeof Sizzle === "function") {

  d3_select = function(s, n) { return Sizzle(s, n)[0]; };

  d3_selectAll = function(s, n) { return Sizzle.uniqueSort(Sizzle(s, n)); };

}

var d3_selectionPrototype = [];

d3.selection = function() {

  return d3_selectionRoot;

};

d3.selection.prototype = d3_selectionPrototype;