Fix visualize_tests.py JSON not serializable
Fix visualize_tests.py JSON not serializable

e-koch/mpld3,etgalloway/mpld3,mpld3/mpld3,mpld3/mpld3,jakevdp/mpld3,etgalloway/mpld3,e-koch/mpld3,aflaxman/mpld3,kdheepak89/mpld3,aflaxman/mpld3,jakevdp/mpld3,kdheepak89/mpld3