fix coding style

research/object_detection/models/faster_rcnn_resnet_v1_fpn_keras_feature_extractor.py

@@ -66,6 +66,16 @@ class ResnetFPN(tf.keras.layers.Layer):
     self._base_fpn_max_level = base_fpn_max_level
 
   def call(self, inputs):
+    """Create ResnetFPN layer.
+
+    Args:
+      inputs: A [batch, height_out, width_out, channels] float32 tensor
+        representing a batch of images.
+
+    Return:
+      feature_maps: A list of tensors with shape [batch, height, width, depth]
+        represent extracted features.
+    """
     inputs = ops.pad_to_multiple(inputs, self.pad_to_multiple)
     backbone_outputs = self.classification_backbone(inputs)