public Builder clearSourceDisk() {
      sourceDisk_ = getDefaultInstance().getSourceDisk();
      bitField0_ = (bitField0_ & ~0x00000001);
      onChanged();
      return this;
    }
<pre>
Specifies the full path to an existing disk.
For example: "projects/my-project/zones/us-central1-c/disks/my-disk".
</pre>

<code>string source_disk = 3;</code>

@return This builder for chaining.
java-tpu/proto-google-cloud-tpu-v2/src/main/java/com/google/cloud/tpu/v2/AttachedDisk.java