add has_duplicates and all_unique

snippets/all_unique.md

@@ -0,0 +1,16 @@
+### all_unique
+
+Checks a flat list for all unique values. Returns True if list values are all unique and False if list values aren't all unique.
+
+This function compares the length of the list with length of the set() of the list. set() removes duplicate values from the list.
+
+``` python
+def all_unique(lst):
+    return len(lst) == len(set(lst))
+```
+
+``` python
+x = [1,2,3,4,5,6]
+all_unique(x) # result
+True
+```