[Doc] Fix invalid symbols in docstring

mmcv/ops/correlation.py

@@ -118,20 +118,20 @@ class Correlation(nn.Module):
 
     There are two batched tensors with shape :math:`(N, C, H, W)`,
     and the correlation output's shape is
-    :math:`(N, \text{max_displacement} \times 2+1,
-    \text{max_displacement} \times 2+1,
+    :math:`(N, \text{max\_displacement} \times 2+1,
+    \text{max\_displacement} \times 2+1,
     H_{out}, W_{out})`
 
     where
 
     .. math::
         H_{out} = \left\lfloor\frac{H_{in}  + 2 \times \text{padding} -
-                \text{dilation} \times (\text{kernel_size} - 1) - 1}
+                \text{dilation} \times (\text{kernel\_size} - 1) - 1}
                 {\text{stride}} + 1\right\rfloor
 
     .. math::
         W_{out} = \left\lfloor\frac{W_{in}  + 2 \times \text{padding} -
-            \text{dilation} \times (\text{kernel_size} - 1) - 1}
+            \text{dilation} \times (\text{kernel\_size} - 1) - 1}
             {\text{stride}} + 1\right\rfloor
 
     the correlation item :math:`(N_i, dy, dx)` is formed by taking the sliding

mmcv/ops/group_points.py

@@ -71,7 +71,7 @@ class QueryAndGroup(nn.Module):
             center_xyz (Tensor): (B, npoint, 3) coordinates of the centriods.
             features (Tensor): (B, C, N) Descriptors of the features.
 
-        Return：
+        Return:
             Tensor: (B, 3 + C, npoint, sample_num) Grouped feature.
         """
         # if self.max_radius is None, we will perform kNN instead of ball query

mmcv/ops/points_sampler.py

@@ -95,7 +95,7 @@ class PointsSampler(nn.Module):
             points_xyz (Tensor): (B, N, 3) xyz coordinates of the features.
             features (Tensor): (B, C, N) Descriptors of the features.
 
-        Return：
+        Return:
             Tensor: (B, npoint, sample_num) Indices of sampled points.
         """
         indices = []
@@ -166,7 +166,7 @@ class FSSampler(nn.Module):
         super().__init__()
 
     def forward(self, points, features, npoint):
-        """Sampling points with FS_Sampling."""
+        r"""Sampling points with FS\_Sampling."""
         assert features is not None, \
             'feature input to FS_Sampler should not be None'
         ffps_sampler = FFPSSampler()