import torch.nn as nn
from transformers import RobertaModel


class RoBERTaClassifier(nn.Module):
    def __init__(self, num_labels):
        super(RoBERTaClassifier, self).__init__()
        self.roberta = RobertaModel.from_pretrained('roberta-base')
        self.dropout = nn.Dropout(0.2)
        self.linear = nn.Linear(self.roberta.config.hidden_size, num_labels)
        self.sigmoid = nn.Sigmoid()

    def forward(self, input_ids, attention_mask):
        outputs = self.roberta(input_ids=input_ids, attention_mask=attention_mask)
        pooled_output = outputs.pooler_output
        pooled_output = self.dropout(pooled_output)
        logits = self.linear(pooled_output)
        return self.sigmoid(logits)