public Builder clearEmail() {
        bitField0_ = (bitField0_ & ~0x00000004);
        email_ = getDefaultInstance().getEmail();
        onChanged();
        return this;
      }
<code>optional string email = 3;</code>
@return This builder for chaining.
core/src/test/java/com/alibaba/fastjson2/protobuf/PersonOuterClass.java