Rename variables to make the codes more readable

pygmt/helpers/decorators.py

@@ -372,17 +372,18 @@ def new_module(*args, **kwargs):
             """
             New module that parses and replaces the registered aliases.
             """
-            for arg, alias in aliases.items():
-                if alias in kwargs and arg in kwargs:
+            for short_param, long_alias in aliases.items():
+                if long_alias in kwargs and short_param in kwargs:
                     raise GMTInvalidInput(
-                        f"Parameters in short-form ({arg}) and long-form ({alias}) can't coexist."
+                        f"Parameters in short-form ({short_param}) and "
+                        f"long-form ({long_alias}) can't coexist."
                     )
-                if alias in kwargs:
-                    kwargs[arg] = kwargs.pop(alias)
-                elif arg in kwargs:
+                if long_alias in kwargs:
+                    kwargs[short_param] = kwargs.pop(long_alias)
+                elif short_param in kwargs:
                     msg = (
-                        f"Short-form parameter ({arg}) is not recommended. "
-                        f"Use long-form parameter '{alias}' instead."
+                        f"Short-form parameter ({short_param}) is not recommended. "
+                        f"Use long-form parameter '{long_alias}' instead."
                     )
                     warnings.warn(msg, category=SyntaxWarning, stacklevel=2)
             return module_func(*args, **kwargs)