Policy.ReadWrite.CrossTenantAccess

const options = {
	authProvider,
};

const client = Client.init(options);

const crossTenantAccessPolicyConfigurationPartner = {
  tenantId: '3d0f5dec-5d3d-455c-8016-e2af1ae4d31a',
  b2bDirectConnectOutbound: 
  {
    usersAndGroups: 
    {
      accessType: 'blocked',
      targets: [
        {
            target: '6f546279-4da5-4b53-a095-09ea0cef9971',
            targetType: 'group'
        }
      ]
    }
  },
  b2bDirectConnectInbound: 
  {
    applications: 
    {
      accessType: 'allowed',
      targets: [
        {
            target: 'Office365',
            targetType: 'application'
        }
      ]
    }
  }
};

await client.api('/policies/crossTenantAccessPolicy/partners')
	.post(crossTenantAccessPolicyConfigurationPartner);

Import-Module Microsoft.Graph.Identity.SignIns

$params = @{
	tenantId = "3d0f5dec-5d3d-455c-8016-e2af1ae4d31a"
	b2bDirectConnectOutbound = @{
		usersAndGroups = @{
			accessType = "blocked"
			targets = @(
				@{
					target = "6f546279-4da5-4b53-a095-09ea0cef9971"
					targetType = "group"
				}
			)
		}
	}
	b2bDirectConnectInbound = @{
		applications = @{
			accessType = "allowed"
			targets = @(
				@{
					target = "Office365"
					targetType = "application"
				}
			)
		}
	}
}

New-MgPolicyCrossTenantAccessPolicyPartner -BodyParameter $params

# Code snippets are only available for the latest version. Current version is 1.x
from msgraph import GraphServiceClient
from msgraph.generated.models.cross_tenant_access_policy_configuration_partner import CrossTenantAccessPolicyConfigurationPartner
from msgraph.generated.models.cross_tenant_access_policy_b2_b_setting import CrossTenantAccessPolicyB2BSetting
from msgraph.generated.models.cross_tenant_access_policy_target_configuration import CrossTenantAccessPolicyTargetConfiguration
from msgraph.generated.models.cross_tenant_access_policy_target_configuration_access_type import CrossTenantAccessPolicyTargetConfigurationAccessType
from msgraph.generated.models.cross_tenant_access_policy_target import CrossTenantAccessPolicyTarget
from msgraph.generated.models.cross_tenant_access_policy_target_type import CrossTenantAccessPolicyTargetType
# To initialize your graph_client, see https://learn.microsoft.com/en-us/graph/sdks/create-client?from=snippets&tabs=python
request_body = CrossTenantAccessPolicyConfigurationPartner(
	tenant_id = "3d0f5dec-5d3d-455c-8016-e2af1ae4d31a",
	b2b_direct_connect_outbound = CrossTenantAccessPolicyB2BSetting(
		users_and_groups = CrossTenantAccessPolicyTargetConfiguration(
			access_type = CrossTenantAccessPolicyTargetConfigurationAccessType.Blocked,
			targets = [
				CrossTenantAccessPolicyTarget(
					target = "6f546279-4da5-4b53-a095-09ea0cef9971",
					target_type = CrossTenantAccessPolicyTargetType.Group,
				),
			],
		),
	),
	b2b_direct_connect_inbound = CrossTenantAccessPolicyB2BSetting(
		applications = CrossTenantAccessPolicyTargetConfiguration(
			access_type = CrossTenantAccessPolicyTargetConfigurationAccessType.Allowed,
			targets = [
				CrossTenantAccessPolicyTarget(
					target = "Office365",
					target_type = CrossTenantAccessPolicyTargetType.Application,
				),
			],
		),
	),
)

result = await graph_client.policies.cross_tenant_access_policy.partners.post(request_body)