FIX: idwtn should treat None coefficients as described in the docstring.

This change also makes is consistent with the existing idwt2 behavior

Author: grlee77

pywt/_multidim.py

@@ -106,10 +106,6 @@ def idwt2(coeffs, wavelet, mode='symmetric', axes=(-2, -1)):
         raise ValueError("Expected 2 axes")
 
     coeffs = {'aa': LL, 'da': HL, 'ad': LH, 'dd': HH}
-
-    # drop the keys corresponding to value = None
-    coeffs = dict((k, v) for k, v in coeffs.items() if v is not None)
-
     return idwtn(coeffs, wavelet, mode, axes)
 
 
@@ -240,6 +236,9 @@ def idwtn(coeffs, wavelet, mode='symmetric', axes=None):
         wavelet = Wavelet(wavelet)
     mode = Modes.from_object(mode)
 
+    # drop the keys corresponding to value = None
+    coeffs = dict((k, v) for k, v in coeffs.items() if v is not None)
+
     # Raise error for invalid key combinations
     coeffs = _fix_coeffs(coeffs)