RegExpWrapper = function RegExp(pattern, flags) {
	    var thisIsRegExp = this instanceof RegExpWrapper;
	    var patternIsRegExp = isRegexp(pattern);
	    var flagsAreUndefined = flags === undefined;
	    return !thisIsRegExp && patternIsRegExp && pattern.constructor === RegExpWrapper && flagsAreUndefined ? pattern
	      : inheritIfRequired(CORRECT_NEW
	        ? new NativeRegExp(patternIsRegExp && !flagsAreUndefined ? pattern.source : pattern, flags)
	        : NativeRegExp((patternIsRegExp = pattern instanceof RegExpWrapper)
	          ? pattern.source
	          : pattern, patternIsRegExp && flagsAreUndefined ? regexpFlags.call(pattern) : flags)
	      , thisIsRegExp ? this : RegExpPrototype, RegExpWrapper);
	  }
Multiply one DataFrame n x p and a second p x n.
@param {DataFrame} df The second DataFrame to multiply.
@returns {DataFrame} A new n x n DataFrame resulting to the product of two DataFrame.
@example
df.matrix.dot(df)