move import to avoid infinte recursion (filter import peak that import feature that import filter)

skimage/filter/__init__.py

@@ -1,7 +1,6 @@
 from .lpi_filter import inverse, wiener, LPIFilter2D
 from ._gaussian import gaussian_filter
 # Backward compatibility v<0.11
-from ..feature import canny
 from .edges import (sobel, hsobel, vsobel, scharr, hscharr, vscharr, prewitt,
                     hprewitt, vprewitt, roberts, roberts_positive_diagonal,
                     roberts_negative_diagonal)
@@ -10,6 +9,7 @@ from ._gabor import gabor_kernel, gabor_filter
 from .thresholding import (threshold_adaptive, threshold_otsu, threshold_yen,
                            threshold_isodata)
 from . import rank
+from ..feature import canny
 
 
 from skimage._shared.utils import deprecated