str.find (sub, start, end)
sub: It`s the substring which needs to be searched in the given string.
start: Starting position where sub is needs to be checked within the string.
end: Ending position where suffix is needs to be checked within the string.
NOTE. If no start and end indices are supplied, then it defaults to 0 and length-1 as start and end indices, where end indices are not included in our search.
returns the lowest index of the substring if it is found in given string. If it`s not found then it returns -1.
Substring `geeks` found at index: 0 Substring` for `found at index: 6 Doesn`t contains given substring
10 -1 -1 6