Add expand_pairlist method

freqtrade/plugins/pairlist/pairlist_helpers.py

@@ -0,0 +1,18 @@
+import re
+from typing import List
+
+
+def expand_pairlist(wildcardpl: List[str], available_pairs: List[str]) -> List[str]:
+    """
+    TODO: Add docstring here
+    """
+    result = []
+    for pair_wc in wildcardpl:
+        try:
+            comp = re.compile(pair_wc)
+            result += [
+                pair for pair in available_pairs if re.match(comp, pair)
+            ]
+        except re.error as err:
+            raise ValueError(f"Wildcard error in {pair_wc}, {err}")
+    return result