Create Picklist Dependency by APEX

Create Picklist Dependency by APEX.cls

public with sharing class UpdatePicklistDependency {
    // A1 is the dependent value, A is the controlling value
    // which means A1 is controller by A, 1 => Many
    private static Map<String, List<String>> relationships = new Map<String, List<String>> {
        'A1' => new List<String>{'A'},
        'A2' => new List<String>{'A'},
        'B1' => new List<String>{'B'},
        'B2' => new List<String>{'B'},
        'C1' => new List<String>{'C'},
        'C2' => new List<String>{'C'},
        'C3' => new List<String>{'C'}
    };
    
    // Prepare the Org to call the Metadata API on the current user permissions 
    public static MetadataService.MetadataPort createService(){
        MetadataService.MetadataPort service = new MetadataService.MetadataPort();
        service.SessionHeader = new MetadataService.SessionHeader_element();
        service.SessionHeader.sessionId = UserInfo.getSessionId();
        return service;
    }
    
    
    public static MetadataService.SaveResult[] updateDependency() {
        MetadataService.MetadataPort service = createService();
        MetadataService.SaveResult[] results = service.updateMetadata(
            new List<MetadataService.Metadata> {
                getControllingField()
            }
        );

        results = service.updateMetadata(
            new List<MetadataService.Metadata> {
                getDependentField()
            }
        );

        return results;
    }

    private static MetadataService.CustomField getControllingField() {
        MetadataService.CustomField customField = new MetadataService.CustomField(); 
        customField.fullName = 'Expense__c.Controller__c';
        customField.label = 'Controller';
        customField.type_x = 'Picklist'; 
        
        /* Prepare the picklist with Controlling pickList field */
        MetadataService.Picklist pt = new metadataservice.Picklist();
        pt.sorted = true;
        pt.picklistValues = new list<metadataservice.PicklistValue>();
        
        Set<String> values = new Set<String>();
        for (List<String> vals : relationships.values()) {
            for (String val : vals) {
                values.add(val);
            }
        }

        for(String key : values){
            MetadataService.PicklistValue plValue = new MetadataService.PicklistValue();
            plValue.fullName = key; // Dependent picklist value
            plValue.isActive = true;
            plValue.default_x = false; // Set default to false
            pt.picklistValues.add(plValue);
        }

        customField.picklist = pt;

        return customField;
    }

    private static MetadataService.CustomField getDependentField() {
        MetadataService.CustomField customField = new MetadataService.CustomField(); 
        customField.fullName = 'Expense__c.Dependent__c';
        customField.label = 'Dependent';
        customField.type_x = 'Picklist'; 
        
        /* Prepare the picklist with Controlling pickList field */
        MetadataService.Picklist pt = new metadataservice.Picklist();
        pt.sorted= true;
        pt.controllingField = 'Controller__c';

        pt.picklistValues = new list<metadataservice.PicklistValue>();
        for(String key : relationships.keySet()){
            MetadataService.PicklistValue plValue = new MetadataService.PicklistValue();
            plValue.fullName=key; // Dependent picklist value
            plValue.isActive = true;
            plValue.default_x=false; // Set default to false
            plValue.controllingFieldValues = relationships.get(key);
            pt.picklistValues.add(plValue);       
        } 
        customField.picklist = pt;

        return customField;
    }
}

This doesn't work now. There's no field called "picklist" on CustomField.