Explanation
This JSON can be written as follows:
{
'switch': {
'name': 'dist1',
'interfaces': ['gig1', 'gig2', 'gig3']
}
}

SW1 has been configured with the following commands:
SW1(config)#monitor session 1 source remote vlan 50 SW1(config)#monitor session 2 source interface fa0/14 SW1(config)#monitor session 2 destination interface fa0/15
The session 1 on SW1 was configured for Remote SPAN (RSPAN) while session 2 was configured for local SPAN. For RSPAN we need to configure the destination port to complete the configuration.
Note: In fact we cannot create such a session like session 1 because if we only configure -Source RSPAN VLAN 50 (with the command -monitor session 1 source remote vlan 50) then we will receive a -Type: Remote Source Session (not -Remote Destination Session).