2. Summary of Significant Accounting Policies (Details Narrative) - USD ($) $ in Thousands	12 Months Ended
Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019	May 02, 2018
Restricted cash	$ 350	$ 350	$ 1,150
Adjustment to accumulated deficit	(559,859)	(571,071)
Revenue recognized for which the contract liability was recorded in the prior year	27,300	13,600
Increase decrease in revenues	1,100	(1,500)
Allowance for doubtful accounts	0	0
Interest expense on construction in progress	0	0
Depreciation and amortization	3,453	3,091	$ 2,746
Impairment of long-lived assets	0	0
Capitalized software implementation costs	900	0
Cash equivalents	158,800	27,600
Senior convertible notes balance	$ 143,500	$ 0
Adoption of ASC 606 [Member]
Adjustment to accumulated deficit				$ 2,700
Sales Revenue Net [Member] \| UNITED STATES
Concentration risk percentage	100.00%	99.00%	95.00%
Accounts Receivable [Member] \| Six Customers [Member]
Concentration risk percentage	98.00%	98.00%
Contract Assets [Member] \| Six Customers [Member]
Concentration risk percentage	97.00%
Contract Assets [Member] \| Eight Customers [Member]
Concentration risk percentage		96.00%

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