First sample generated methods

Everything in the body of BigQueryClient.DatasetLabels.cs after the first line (comment) is autogenerated.

The remaining work for these features will be:

- Implementation in BigQueryDatasetImpl
- Options test
- Snippets
- Methods in BigQueryDataset.cs (we may improve the generator to do these later...)
- Integration tests

apis/Google.Cloud.BigQuery.V2/Google.Cloud.BigQuery.V2.GenerateOverloads/Methods/ClearDatasetLabels.xml

@@ -0,0 +1,13 @@
+<Method Name="ClearDatasetLabels"
+        TargetType="Dataset"
+        ReturnType="IDictionary&lt;string, string&gt;">
+  <Options Type="ModifyLabelsOptions" />
+
+  <Comments>
+    <summary>
+      Clears all labels on {target}.
+    </summary>
+    <returns>A dictionary with the labels on the dataset before they were cleared.</returns>
+  </Comments>
+
+</Method>

apis/Google.Cloud.BigQuery.V2/Google.Cloud.BigQuery.V2.GenerateOverloads/Methods/ModifyDatasetLabels.xml

@@ -0,0 +1,26 @@
+<Method Name="ModifyDatasetLabels"
+        TargetType="Dataset"
+        ReturnType="IDictionary&lt;string, string&gt;">
+  <Options Type="ModifyLabelsOptions" />
+
+  <AdditionalParameters>
+    <Parameter Name="labels" Type="IDictionary&lt;string, string&gt;" Comment="The labels to set. Must contain at least one entry; keys must not be null, but values may be (indicating label removal)." />
+  </AdditionalParameters>
+
+  <Comments>
+    <summary>
+      Sets or removes one or more labels on {target}.
+    </summary>
+    <remarks>
+      Each entry in <paramref name="labels"/> is treated as a label to set or remove. If the value is null,
+      it will be removed from the bucket; otherwise, it will be set/added. Labels which do not have an entry
+      in the dictionary will be ignored.
+    </remarks>
+    <returns>
+      A dictionary with the same keys as <paramref name="labels"/>, and values indicating the corresponding label value
+      before this operation completed. Labels which weren't present on the bucket before the modification have corresponding
+      null values in the returned dictionary.
+    </returns>
+  </Comments>
+
+</Method>

apis/Google.Cloud.BigQuery.V2/Google.Cloud.BigQuery.V2.GenerateOverloads/Methods/RemoveDatasetLabel.xml

@@ -0,0 +1,18 @@
+<Method Name="RemoveDatasetLabel"
+        TargetType="Dataset"
+        ReturnType="string">
+  <Options Type="ModifyLabelsOptions" />
+
+  <AdditionalParameters>
+    <Parameter Name="labelName" Type="string" Comment="The name of the label. Must not be null." />
+  </AdditionalParameters>
+
+  <Comments>
+    <summary>
+      Removes a label from a bucket, if it previously existed. It is not an error to
+      attempt to remove a label that doesn't already exist.
+    </summary>
+    <returns>The previous value of the label, or <c>null</c> if the label was not previously set.</returns>
+  </Comments>
+
+</Method>

apis/Google.Cloud.BigQuery.V2/Google.Cloud.BigQuery.V2.GenerateOverloads/Methods/SetDatasetLabel.xml

@@ -0,0 +1,24 @@
+<Method Name="SetDatasetLabel"
+        TargetType="Dataset"
+        ReturnType="string">
+  <Options Type="ModifyLabelsOptions" />
+
+  <AdditionalParameters>
+    <Parameter Name="labelName" Type="string" Comment="The name of the label. Must not be null." />
+    <Parameter Name="labelValue" Type="string" Comment="The new value of the label. Must not be null." />
+  </AdditionalParameters>
+
+  <Comments>
+    <summary>
+      Sets the value for a single label on a dataset. The label will be added if it does
+      not exist, or updated if it already exists.
+    </summary>
+    <remarks>
+      <para>
+        The dataset is first fetched to retrieve the current values, then a patch call is made.
+      </para>
+    </remarks>
+    <returns>The previous value of the label, or <c>null</c> if the label was not previously set.</returns>
+  </Comments>
+
+</Method>

apis/Google.Cloud.BigQuery.V2/Google.Cloud.BigQuery.V2.GenerateOverloads/generateoverloads.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+declare -r CLIENT=../Google.Cloud.BigQuery.V2/BigQueryClient
+dotnet run -- Methods/SetDatasetLabel.xml $CLIENT.DatasetLabels.cs
+dotnet run -- Methods/RemoveDatasetLabel.xml $CLIENT.DatasetLabels.cs
+dotnet run -- Methods/ClearDatasetLabels.xml $CLIENT.DatasetLabels.cs
+dotnet run -- Methods/ModifyDatasetLabels.xml $CLIENT.DatasetLabels.cs