fix: fix fetch qmax

Author: stevenhua0320

src/diffpy/srmise/pdfpeakextraction.py

@@ -247,7 +247,7 @@ def defaultvars(self, *args):
 
         # Enable "dg" as alias for "effective_dy"
         if "dg" in args and "effective_dy" not in args:
-            nargs.add("effective_dy")
+            nargs.append("effective_dy")
 
         # Set other defaults
         PeakExtraction.defaultvars(self, *nargs)
@@ -1000,7 +1000,7 @@ def find_qmax(r, y, showgraphs=False):
     new_y = resample(r, y, new_r)
     new_dr = (new_r[-1] - r[0]) / (len(new_r) - 1)
 
-    yfft = np.imag(np.fft.fft(new_y))[: len(new_y) / 2]
+    yfft = np.imag(np.fft.fft(new_y))[: len(new_y) // 2]
 
     d_ratio = stdratio(yfft)