public Builder mergeHeader(com.google.cloud.tasks.v2beta2.HttpTarget.Header value) {
        if (headerBuilder_ == null) {
          if (((bitField0_ & 0x00000001) != 0)
              && header_ != null
              && header_ != com.google.cloud.tasks.v2beta2.HttpTarget.Header.getDefaultInstance()) {
            getHeaderBuilder().mergeFrom(value);
          } else {
            header_ = value;
          }
        } else {
          headerBuilder_.mergeFrom(value);
        }
        if (header_ != null) {
          bitField0_ |= 0x00000001;
          onChanged();
        }
        return this;
      }
<pre>
header embodying a key and a value.
</pre>

<code>.google.cloud.tasks.v2beta2.HttpTarget.Header header = 1;</code>
java-tasks/proto-google-cloud-tasks-v2beta2/src/main/java/com/google/cloud/tasks/v2beta2/HttpTarget.java