docs: def get_coordinate_offset(self, other_reading):
          """
          Calculates the offsets between readings' coordinate systems.
  
          Args:
            other_reading: ossos.astrom.SourceReading
              The reading to compare coordinate systems with.
  
          Returns:
            (offset_x, offset_y):
              The x and y offsets between this reading and the other reading's
              coordinate systems.
          """
          my_x, my_y = self.reference_source_point
          other_x, other_y = other_reading.reference_source_point
          return my_x - other_x, my_y - other_y