function samePolicy( dtypes ) {
	var dt;
	var i;

	dt = dtypes[ 0 ];
	for ( i = 1; i < dtypes.length; i++ ) {
		// When the policy is "same", we require that all data types (both input and output) be the same...
		if ( dtypes[ i ] !== dt ) {
			throw new Error( format( 'invalid argument. Unable to resolve an output data type. The output data type policy is "same" and yet the input data types are not equal. Data types: [%s].', join( dtypes, ', ' ) ) );
		}
	}
	return dt;
}
Applies the "same" policy by returning the common input data type.

@private
@param {StringArray} dtypes - input ndarray data types
@throws {Error} invalid data types
@returns {string} output ndarray data type