import torch
from torch import nn
from transformers import BertModel

class BertClassifier(nn.Module):
    def __init__(self, dropout=0.3):
        super(BertClassifier, self).__init__()
        self.bert = BertModel.from_pretrained("bert-base-uncased")
        self.dropout = nn.Dropout(dropout)
        self.classifier = nn.Linear(self.bert.config.hidden_size, 4)

    def forward(self, input_ids, attention_mask):
        outputs = self.bert(input_ids=input_ids, attention_mask=attention_mask)
        pooled_output = outputs.pooler_output
        dropped = self.dropout(pooled_output)
        return self.classifier(dropped)