Annual report pursuant to Section 13 and 15(d)

Stockholders' Equity - Schedule of Outstanding and Exercisable Warrants (Details)

v3.21.2
Stockholders' Equity - Schedule of Outstanding and Exercisable Warrants (Details) - $ / shares
12 Months Ended
Apr. 30, 2021
Apr. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 1,214,473  
Exercisable (in shares) 1,032,411 2,734,899
Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 374,174 566,223
Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Exercisable (in shares) 374,174  
Warrant | Warrant    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Outstanding (in shares) 374,174  
Warrant | $4.89    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 4.89  
Maximum exercise price (in dollars per share) 4.89  
Weighted average exercise price (in dollars per share) $ 4.89  
Outstanding (in shares) 50,000  
Weighted average exercise price (in dollars per share) $ 4.89  
Weighted average remaining life (in years) 3 years 5 months 8 days  
Exercisable (in shares) 50,000  
Warrant | $6.00    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 6.00  
Maximum exercise price (in dollars per share) 6.00  
Weighted average exercise price (in dollars per share) $ 6.00  
Outstanding (in shares) 100,000  
Weighted average exercise price (in dollars per share) $ 6.00  
Weighted average remaining life (in years) 3 years 1 month 2 days  
Exercisable (in shares) 100,000  
Warrant | $6.87    
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]    
Minimum exercise price (in dollars per share) $ 6.87  
Maximum exercise price (in dollars per share) 6.87  
Weighted average exercise price (in dollars per share) $ 6.87  
Outstanding (in shares) 224,174  
Weighted average exercise price (in dollars per share) $ 6.87  
Weighted average remaining life (in years) 1 year 5 months 23 days  
Exercisable (in shares) 224,174