function dependentsCount( slug, options, clbk ) {
	var opts;
	var err;
	var cb;
	if ( !isString( slug ) ) {
		throw new TypeError( format( 'invalid argument. First argument must be a string. Value: `%s`.', slug ) );
	}
	opts = defaults();
	if ( arguments.length > 2 ) {
		err = validate( opts, options );
		if ( err ) {
			throw err;
		}
		cb = clbk;
	} else {
		cb = options;
	}
	if ( !isFunction( cb ) ) {
		throw new TypeError( format( 'invalid argument. Last argument must be a function. Value: `%s`.', cb ) );
	}
	opts.slug = slug;
	opts.pathname = replace( opts.pathname, '{slug}', slug );
	resolve( opts, done );

	/**
	* Callback invoked after resolving the number of dependents.
	*
	* @private
	* @param {(Error|null)} error - error object
	* @param {ObjectArray} [data] - results
	* @returns {void}
	*/
	function done( error, data ) {
		if ( error ) {
			return cb( error );
		}
		cb( error, data );
	}
}
Returns the number of dependents for a package from GitHub.

@param {string} slug - repository slug
@param {Options} [options] - options
@param {string} [options.useragent] - user agent string
@param {Callback} clbk - callback to invoke upon query completion
@throws {TypeError} first argument must be a string
@throws {TypeError} options argument must be an object
@throws {TypeError} must provide valid options
@throws {TypeError} last argument must be a function

@example
dependentsCount( 'stdlib-js/stdlib', onResponse );

function onResponse( error, data ) {
    if ( error ) {
        throw error;
    }
    console.log( JSON.stringify( data ) );
}