https://www.programiz.com/python-programming/methods/built-in/filter
The filter() method constructs an iterator from elements of an iterable for which a function returns true.
filter () method syntax:
filter(function, iterable)
parameter:
function - function that tests if elements of an iterable returns true or false. If None, the function defaults to Identity function - which returns false if any elements are false.
iterable - iterable which is to be filtered, could be sets, lists, tuples, or containers of any iterators.
return value:
The filter() method returns an iterator that passed the function check for each element in the iterable.
filter () method is equivalent to:
# when function is defined
(element for element in iterable if function(element))
# when function is None
(element for element in iterable if element)