Bug when try to "Load into REPL"

pact-web-interface-example.pact

(define-keyset "test-keyset" (read-keyset "test-keyset"))

(module acct-module "test-keyset"
  @doc "account schema module"

  (defschema account
    @model [(invariant (>= balance 0))]

    balance:integer
    ks:keyset
  )

  (deftable accounts:{account})
)

(interface coin-sig

  "Example Coin Contract"

  (use acct-module)

  (defun transfer (from:string to:string amount:integer)
    @doc   "Transfer money between accounts"
    @model [(property (row-enforced accounts "ks" from))
            (property (> amount 0))
            ;;(property (= 0 (column-delta accounts "balance")))
            ;;(property (<= 0 (cell-delta accounts "balance" from)))
            (property (!= from to)) ]
  )
)

(module test-impl "test-keyset"
  @doc "test if implementing test-sig resolves schema type"

  (use acct-module)
  (implements coin-sig)

  (defun transfer (from:string to:string amount:integer)
    (with-read accounts from { 'balance := from-bal, 'ks := from-ks }
    (with-read accounts to { 'balance := to-bal }
      (enforce-keyset from-ks)
      (enforce (>= from-bal amount) "Insufficient Funds")
      (enforce (> amount 0)         "Non-positive amount")
      (enforce (!= from to)         "Sender is the recipient")
      (update accounts from { "balance": (- 0 amount) })
      (update accounts to   { "balance": (+ to-bal amount) }))))
)