add optional + default in pyx docstring

skimage/transform/_hough_transform.pyx

@@ -31,10 +31,10 @@ def hough_circle(cnp.ndarray img,
         Input image with nonzero values representing edges.
     radius : ndarray
         Radii at which to compute the Hough transform.
-    normalize : boolean, optional
+    normalize : boolean, optional (default True)
         Normalize the accumulator with the number
-        of pixels used to draw the radius
-    full_output : boolean, optional
+        of pixels used to draw the radius.
+    full_output : boolean, optional (default False)
         Extend the output size by twice the largest
         radius in order to detect centers outside the
         input picture.

skimage/transform/_warps_cy.pyx

@@ -67,17 +67,17 @@ def _warp_fast(cnp.ndarray image, cnp.ndarray H, output_shape=None,
         Input image.
     H : array of shape ``(3, 3)``
         Transformation matrix H that defines the homography.
-    output_shape : tuple (rows, cols)
-        Shape of the output image generated.
-    order : {0, 1}
+    output_shape : tuple (rows, cols), optional
+        Shape of the output image generated (default None).
+    order : {0, 1}, optional
         Order of interpolation::
         * 0: Nearest-neighbour interpolation.
         * 1: Bilinear interpolation (default).
-        * 2: Biquadratic interpolation (default).
+        * 2: Biquadratic interpolation.
         * 3: Bicubic interpolation.
-    mode : {'constant', 'reflect', 'wrap', 'nearest'}
-        How to handle values outside the image borders.
-    cval : string
+    mode : {'constant', 'reflect', 'wrap', 'nearest'}, optional
+        How to handle values outside the image borders (default is constant).
+    cval : string, optional (default 0)
         Used in conjunction with mode 'C' (constant), the value
         outside the image boundaries.