When all else fails READ THE INSTRUCTIONS!  https://www.irs.gov/pub/irs-prior/i1065sk1--2018.pdf

Box 10. Net Section 1231 Gain (Loss) 

The amount in box 10 is generally passive if it is from a: 

• Rental activity, or 

• Trade or business activity in which you didn't materially participate. 

However, an amount from a rental real estate activity isn't from a passive activity if you were a real estate professional (defined earlier) and you materially participated in the activity. 

If the amount is either (a) a loss that isn't from a passive activity or (b) a gain, report it on line 2, column (g), of Form 4797, Sales of Business Property. Do not complete columns (b) through (f) on line 2 of Form 4797. Instead, enter “From Schedule K-1 (Form 1065)” across these columns. 

If the amount is a loss from a passive activity, see Passive Loss Limitations in the Instructions for Form 4797. Report the loss following the Instructions for Form 8582 to figure how much of the loss is allowed on Form 4797. However, if the box in item D is checked, report the loss following the rules for Publicly traded partnerships, earlier. 

If the partnership had net section 1231 gain (loss) from more than one activity, it will attach a statement that will identify the section 1231 gain (loss) from each activity. 

If you have any foreign source net section 1231 gain (loss), see the instructions for box 16, later. net section 1231 gain (loss), see the instructions for box 16, later