add header formatting method

PyTeX/format/constants.py

@@ -0,0 +1,3 @@
+INFILE_CONFIG_BEGIN_CONFIG = 'config'
+INFILE_CONFIG_END_CONFIG = 'endconfig'
+PYTEX_CONFIG_FILE_EXTENSION = '.conf'

PyTeX/format/pytex_formatter.py

@@ -115,3 +115,8 @@ class PyTeXFormatter(FormatterIF):
                 ## TODO handle rest
 
         return self._header
+
+    def format_header(self, **kwargs) -> None:
+        self._header = self.header.format(
+            **kwargs
+        )  # TODO: add standard keywords here