'How Can I fix "Can only add LpConstraintVar, LpConstraint, LpAffineExpression or True objects" error

Currently I have an LP model and while I'm trying to run it, the constraint

for i in DEMANDPOINT:
    prob += (lpSum(z[i][j]) == 1 for j in FACILITY5)

causes this error to pop up.

TypeError: Can only add LpConstraintVar, LpConstraint, LpAffineExpression or True objects

How can I fix this? Thanks in advance

python variables pulp

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