Add SFG generator for DIF FFT

b_asic/sfg_generators.py

@@ -378,6 +378,18 @@ def direct_form_2_iir(
 
 
 def radix_2_dif_fft(points: int) -> SFG:
+    """Generates a radix-2 decimation-in-frequency FFT structure.
+
+    Parameters
+    ----------
+    points : int
+        Number of points for the FFT, needs to be a positive power of 2.
+
+    Returns
+    -------
+    SFG
+        Signal Flow Graph
+    """
     if points < 0:
         raise ValueError("Points must be positive number.")
     if points & (points - 1) != 0: