function iterFlow( methods ) {
	var keys;
	var k;
	var f;
	var i;
	if ( !isObject( methods ) ) {
		throw new TypeError( format( 'invalid argument. Must provide an object. Value: `%s`.', methods ) );
	}
	/**
	* Fluent interface iterator constructor.
	*
	* @private
	* @constructor
	* @param {Iterator} iterator - source iterator
	* @throws {TypeError} must provide an iterator
	* @returns {FluentIterator} a "fluent" iterator
	*/
	function FluentIterator( iterator ) {
		if ( !( this instanceof FluentIterator ) ) {
			return new FluentIterator( iterator );
		}
		if ( !isIteratorLike( iterator ) ) {
			throw new TypeError( format( 'invalid argument. Must provide an iterator. Value: `%s`.', iterator ) );
		}
		setNonEnumerableReadOnly( this, '_source', iterator );
		setNonEnumerable( this, '_done', false );
		return this;
	}

	/**
	* Returns an iterator protocol-compliant object containing the next iterated value.
	*
	* @private
	* @throws {TypeError} `this` must be a fluent interface iterator
	* @returns {Object} iterator protocol-compliant object
	*/
	setNonEnumerableReadOnly( FluentIterator.prototype, 'next', function next() {
		if ( !(this instanceof FluentIterator) ) {
			throw new TypeError( 'invalid invocation. `this` is not a fluent interface iterator.' );
		}
		if ( this._done ) {
			return {
				'done': true
			};
		}
		return this._source.next();
	});

	/**
	* Finishes an iterator.
	*
	* @private
	* @param {*} [value] - value to return
	* @throws {TypeError} `this` must be a fluent interface iterator
	* @returns {Object} iterator protocol-compliant object
	*/
	setNonEnumerableReadOnly( FluentIterator.prototype, 'return', function finish( value ) {
		if ( !(this instanceof FluentIterator) ) {
			throw new TypeError( 'invalid invocation. `this` is not a fluent interface iterator.' );
		}
		this._done = true;
		if ( arguments.length ) {
			return {
				'value': value,
				'done': true
			};
		}
		return {
			'done': true
		};
	});

	// If an environment supports `Symbol.iterator`, make the iterator iterable:
	if ( iteratorSymbol ) {
		/**
		* Returns the current iterator.
		*
		* ## Notes
		*
		* -   This method allows the iterator to be iterable and thus able to be consumed, e.g., in `for..of` loops.
		*
		* @private
		* @returns {Iterator} iterator
		*/
		setNonEnumerableReadOnly( FluentIterator.prototype, iteratorSymbol, function factory() { // eslint-disable-line max-len
			return this;
		});
	}

	/**
	* Wraps an iterator function as a fluent interface method.
	*
	* @private
	* @param {Function} iterFcn - iterator function
	* @returns {Function} method wrapper
	*/
	function createMethod( iterFcn ) {
		return method;

		/**
		* Iterator function wrapper.
		*
		* @private
		* @param {...*} [args] - method arguments
		* @throws {TypeError} `this` must be a fluent interface iterator
		* @returns {Iterator} iterator
		*/
		function method() {
			var args;
			var out;
			var i;

			if ( !(this instanceof FluentIterator) ) {
				throw new TypeError( 'invalid invocation. `this` is not a fluent interface iterator.' );
			}
			args = [ this._source ];
			for ( i = 0; i < arguments.length; i++ ) {
				args.push( arguments[ i ] );
			}
			out = iterFcn.apply( null, args );

			// If the iterator function returns an iterator, in order to support subsequent chaining, we need to create a new fluent interface instance...
			if ( isIteratorLike( out ) ) {
				return new FluentIterator( out );
			}
			return out;
		}
	}

	// Bind the provided iterator functions to the constructor prototype...
	keys = objectKeys( methods );
	for ( i = 0; i < keys.length; i++ ) {
		k = keys[ i ];
		f = methods[ k ];
		if ( !isFunction( f ) ) {
			throw new TypeError( format( 'invalid argument. Object property values must be functions. Key: `%s`. Value: `%s`.', k, f ) );
		}
		setNonEnumerableReadOnly( FluentIterator.prototype, k, createMethod( f ) ); // eslint-disable-line max-len
	}

	return FluentIterator;
}
Returns a constructor for creating a fluent interface for chaining together iterator methods.

## Notes

-   We assume that each provided iterator function has the following function signature:

    ```text
    function iterFcn( iterator[, ...args] ) {...}
    ```

    where `iterator` is an input iterator and `args` are additional iterator function arguments (if any).

@param {Object} methods - an object mapping method names to iterator functions
@throws {TypeError} must provide an object
@throws {TypeError} object property values must be functions
@returns {Function} constructor

@example
var array2iterator = require( '@stdlib/array/to-iterator' );
var iterHead = require( '@stdlib/iter/head' );
var iterSome = require( '@stdlib/iter/some' );

// Create a "fluent" interface:
var FluentIterator = iterFlow({
    'head': iterHead,
    'some': iterSome
});

// Create a source iterator:
var arr = array2iterator( [ 0, 0, 1, 1, 1, 0, 0, 1, 0, 1 ] );

// Create a new iterator:
var it = new FluentIterator( arr );

var bool = it.head( 5 ).some( 3 );
// returns true

// Create another source iterator:
arr = array2iterator( [ 0, 0, 1, 0, 1, 0, 0, 1, 0, 1 ] );

// Create a new iterator:
it = new FluentIterator( arr );

bool = it.head( 5 ).some( 3 );
// returns false