Document that headers from YAML files should be accepted

python/astro_metadata_translator/translator.py

@@ -991,6 +991,11 @@ def determine_translatable_headers(cls, filename, primary=None):
         `determine_translator()` on the result to work out which translator
         class to then call to obtain the real headers to be used for
         translation.
+
+        If a primary header is given but is associated with a file in a format
+        that is not understood, the primary header is returned and no
+        attempt made to read the file. This situation is commonly encountered
+        with translator test data stored in JSON or YAML format.
         """
         if primary is not None:
             yield primary

python/astro_metadata_translator/translators/decam.py

@@ -335,6 +335,11 @@ def determine_translatable_headers(cls, filename, primary=None):
         `determine_translator()` on the result to work out which translator
         class to then call to obtain the real headers to be used for
         translation.
+
+        If a primary header is given but is associated with a file in a format
+        that is not understood, the primary header is returned and no
+        attempt made to read the file. This situation is commonly encountered
+        with translator test data stored in JSON or YAML format.
         """
         # Circular dependency so must defer import
         from ..headers import merge_headers

python/astro_metadata_translator/translators/megaprime.py

@@ -219,6 +219,11 @@ def determine_translatable_headers(cls, filename, primary=None):
         `determine_translator()` on the result to work out which translator
         class to then call to obtain the real headers to be used for
         translation.
+
+        If a primary header is given but is associated with a file in a format
+        that is not understood, the primary header is returned and no
+        attempt made to read the file. This situation is commonly encountered
+        with translator test data stored in JSON or YAML format.
         """
 
         # If this is not a FITS file return the primary if defined.