Subclass string.Template instead

Author: seisman

pygmt/helpers/decorators.py

@@ -6,6 +6,7 @@
 """
 
 import functools
+import string
 import textwrap
 import warnings
 from inspect import Parameter, signature
@@ -442,21 +443,14 @@ def fmt_docstring(module_func):
     <BLANKLINE>
     """  # noqa: D410,D411
 
-    class _Placeholder(dict):
+    class _MyTemplate(string.Template):
         """
-        A dict subclass that allows missing placeholders in docstrings.
-
-        Related to https://github.com/GenericMappingTools/pygmt/issues/3815.
+        A Template subclass that allows missing placeholders in docstrings.
         """
 
-        def __missing__(self, key):
-            """
-            Return "{key}" for a missing key.
-            """
-            return "{" + key + "}"
-
-    filler_text = _Placeholder()
+        delimiter = ""  # Default delimiter is $.
 
+    filler_text = {}
     if hasattr(module_func, "aliases"):
         aliases = ["**Aliases:**\n"]
         aliases.append(".. hlist::")
@@ -481,7 +475,7 @@ def __missing__(self, key):
     # Dedent the docstring to make it all match the option text.
     docstring = textwrap.dedent(module_func.__doc__)
 
-    module_func.__doc__ = docstring.format_map(filler_text)
+    module_func.__doc__ = _MyTemplate(docstring).safe_substitute(**filler_text)
     return module_func