public Builder setArgTypes(
        int index, java.lang.String value) {
      if (value == null) { throw new NullPointerException(); }
      ensureArgTypesIsMutable();
      argTypes_.set(index, value);
      bitField0_ |= 0x00000004;
      onChanged();
      return this;
    }
<code>repeated string argTypes = 3;</code>
@param index The index to set the value at.
@param value The argTypes to set.
@return This builder for chaining.
remoting/remoting-triple/build/generated/source/proto/main/java/triple/Request.java