Change the "batched" kwarg to "suffix" which have default behavior sa…

…me as the previous version. Add detailed documentation for the "suffix" kwarg.

ddsp/training/data.py

@@ -415,7 +415,7 @@ def __init__(self,
                base_dir,
                instrument_key='tpt',
                split='train',
-               batched='batched'):
+               suffix=None):
     """URMP dataset for either a specific instrument or all instruments.
 
     Args:
@@ -424,22 +424,30 @@ def __init__(self,
         ['all', 'bn', 'cl', 'db', 'fl', 'hn', 'ob', 'sax', 'tba', 'tbn',
         'tpt', 'va', 'vc', 'vn'].
       split: Choices include ['train', 'test'].
-      batched: Choices include ['batched', 'unbatched'].
+      suffix: Choices include [None, 'batched', 'unbatched'], but broadly
+        applies to any suffix adding to the file pattern.
+        When suffix is not None, will add "_suffix" to the file pattern.
+        This option is used in gs://magentadata/datasets/urmp/urmp_20210324.
+        With the "batched" suffix, the dataloader will load tfrecords
+        containing segmented audio samples in 4 seconds. With the "unbatched"
+        suffix, the dataloader will load tfrecords containing unsegmented
+        samples which could be used for learning note sequence in URMP dataset.
+
     """
     self.instrument_key = instrument_key
     self.split = split
     self.base_dir = base_dir
-    self.batched = batched
+    self.suffix = suffix if suffix is None else '_' + suffix
     super().__init__()
 
   @property
   def default_file_pattern(self):
     if self.instrument_key == 'all':
-      file_pattern = 'all_instruments_{}_{}.tfrecord*'.format(
-        self.split, self.batched)
+      file_pattern = 'all_instruments_{}{}.tfrecord*'.format(
+        self.split, self.suffix)
     else:
-      file_pattern = 'urmp_{}_solo_ddsp_conditioning_{}_{}.tfrecord*'.format(
-        self.instrument_key, self.split, self.batched)
+      file_pattern = 'urmp_{}_solo_ddsp_conditioning_{}{}.tfrecord*'.format(
+        self.instrument_key, self.split, self.suffix)
 
     return os.path.join(self.base_dir, file_pattern)