add private module to create model object for acoustics api

opendbm/api_lib/verbal_acoustics/_mfcc.py

@@ -0,0 +1,12 @@
+from opendbm.api_lib.model import AudioModel
+from opendbm.dbm_lib import run_mfcc
+
+
+class MFCC(AudioModel):
+    def __init__(self):
+        super().__init__()
+        self._params = ["aco_mfcc" + str(i) for i in range(1, 13)]
+
+    @AudioModel.prep_func
+    def _fit_transform(self, path, **kwargs):
+        return run_mfcc(path, ".", self.r_config, save=False)