code: func (m *MachinesClient) Create(ctx context.Context, machine *envelope.Machine,
  	memberships []envelope.Membership, token *MachineTokenCreationSegment) (*apitypes.MachineSegment, error) {
  
  	segment := MachineCreationSegment{
  		MachineSegment: apitypes.MachineSegment{
  			Machine:     machine,
  			Memberships: memberships,
  		},
  		Tokens: []MachineTokenCreationSegment{*token},
  	}
  
  	resp := &apitypes.MachineSegment{}
  	err := m.client.RoundTrip(ctx, "POST", "/machines", nil, &segment, &resp)
  	return resp, err
  }
docs: // Create requests the registry to create a MachineSegment.
  //
  // The MachineSegment includes the Machine, it's Memberships, and authorization
  // tokens.