move practice exercise example solutions to .meta/

exercises/practice/nucleotide-count/.meta/example.py

@@ -0,0 +1,18 @@
+NUCLEOTIDES = 'ATCG'
+
+
+def count(strand, abbreviation):
+    _validate(abbreviation)
+    return strand.count(abbreviation)
+
+
+def nucleotide_counts(strand):
+    return {
+        abbr: strand.count(abbr)
+        for abbr in NUCLEOTIDES
+    }
+
+
+def _validate(abbreviation):
+    if abbreviation not in NUCLEOTIDES:
+        raise ValueError('{} is not a nucleotide.'.format(abbreviation))