Add documentation

Author: AdrienVannson

src/betterproto/compile/importing.py

@@ -40,9 +40,12 @@ def parse_source_type_name(
     Split full source type name into package and type name.
     E.g. 'root.package.Message' -> ('root.package', 'Message')
          'root.Message.SomeEnum' -> ('root', 'Message.SomeEnum')
+    
+    The function goes through the symbols that have been defined (names, enums, packages) to find the actual package and
+    name of the object that is referenced.
     """
     if field_type_name[0] != ".":
-        raise RuntimeError
+        raise RuntimeError("relative names are not supported")
     field_type_name = field_type_name[1:]
     parts = field_type_name.split(".")
 

src/betterproto/plugin/models.py

@@ -203,6 +203,9 @@ def __post_init__(self) -> None:
                 raise ValueError(f"`{field_name}` is a required field.")
 
     def ready(self) -> None:
+        """
+        This function is called after all the compilers are created, but before generating the output code.
+        """
         pass
 
     @property