public Builder setMimeTypeBytes(com.google.protobuf.ByteString value) {
      if (value == null) {
        throw new NullPointerException();
      }
      checkByteStringIsUtf8(value);
      mimeType_ = value;
      bitField0_ |= 0x00000001;
      onChanged();
      return this;
    }
<pre>
Required. The file's mime type.
</pre>

<code>string mime_type = 1 [(.google.api.field_behavior) = REQUIRED];</code>

@param value The bytes for mimeType to set.
@return This builder for chaining.
java-translate/proto-google-cloud-translate-v3/src/main/java/com/google/cloud/translate/v3/FileInputSource.java