The begin() function is misleading.

[uodukwe]

In the .h file (Adafruit_MPRLS.h) at line 44 & 45, the begin() function has two arguments: uint8_t i2c_addr and TwoWire *twoWire.

I also see they were assigned:
i2c_addr is assigned to MPRLS_DEFAULT_ADDR
and
twoWire is de-referenced to Wire. Where is this 'Wire' defined or instantiated?
My common sense says it's from 'Wire.h'

[ladyada]

yes - it comes with Arduino.
https://github.com/adafruit/Adafruit_MPRLS/blob/master/Adafruit_MPRLS.cpp#L59