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The Mi Power Bank Pro 10000mAh with a USB Type-C port by Xiaomi uses Qualcomm Quick Charge 3.0 for charging over both its USB Type-C input and USB Type-A output ports. The USB Type-C port only supports charging in meaning it will not charge any connected peripheral since it can only get power supplied by an external charger to charge the battery.  

Unfortunately, a lot of people buy the Mi Power Bank Pro 10000mAh with a USB Type-C port assuming you can use its USB Type-C port to charger USB Type-C phones.

To demonstrate this, we connect a USB Type-C to USB Type-C cable from the Mi Power Bank Pro 10000mAh with a USB Type-C port to a USB Type-C phone like the Google Pixel. Looking at the power graph through the Granite River Labs GRL-USB-PD-A1 App, no charging activity is recorded between the Google phone and the almost well charged Mi power bank. This confirms that the USB Type-C port of the Mi power bank serves only as the input and can't be used to charge your USB Type-C device. Also note that the USB Type-C port does not support any USB Power Delivery communication.