Simplify defaultdict

Author: seisman

pygmt/alias.py

@@ -67,7 +67,7 @@ def convert_aliases():
     params = p_locals.pop("kwargs", {}) | p_locals
 
     # Define a dict to store GMT option flags and arguments
-    kwdict = defaultdict(lambda: "")  # default value is an empty string
+    kwdict = defaultdict(str)  # default value is an empty string
     for alias in p_locals.get("_aliases"):
         value = params.get(alias.name)
         if is_nonstr_iter(value):