Fix declare param_name cutting

ydb_sqlalchemy/sqlalchemy/__init__.py

@@ -354,7 +354,7 @@ def _format_variables(
     def _add_declare_for_yql_stmt_vars_impl(self, statement, parameters_types):
         declarations = "\n".join(
             [
-                f"DECLARE $`{param_name[1:]}` as {str(param_type)};"
+                f"DECLARE $`{param_name[1:] if param_name.startswith('$') else param_name}` as {str(param_type)};"
                 for param_name, param_type in parameters_types.items()
             ]
         )
@@ -415,6 +415,8 @@ def do_executemany(
         context: Optional[DefaultExecutionContext] = None,
     ) -> None:
         operation, parameters = self._prepare_ydb_query(statement, context, parameters, execute_many=True)
+        print(operation)
+        print(parameters)
         cursor.executemany(operation, parameters)
 
     def do_execute(