code: def get_symbol(self) -> str:
      if self.etype == ExpressionType.AGGREGATION_FIRST:
          return "FIRST"
      if self.etype == ExpressionType.AGGREGATION_LAST:
          return "LAST"
      if self.etype == ExpressionType.AGGREGATION_SEGMENT:
          return "SEGMENT"
      if self.etype == ExpressionType.AGGREGATION_SUM:
          return "SUM"
      elif self.etype == ExpressionType.AGGREGATION_COUNT:
          return "COUNT"
      elif self.etype == ExpressionType.AGGREGATION_AVG:
          return "AVG"
      elif self.etype == ExpressionType.AGGREGATION_MIN:
          return "MIN"
      elif self.etype == ExpressionType.AGGREGATION_MAX:
          return "MAX"
      else:
          raise NotImplementedError
  
file_path: evadb/evadb/expression/aggregation_expression.py
imports: from evadb.expression.abstract_expression import AbstractExpression, ExpressionReturnType, ExpressionType
  from evadb.models.storage.batch import Batch
label_desc: Use image node_id 3 for calling the AggregationExpression obj's underlying member method code with example usage: obj.get_symbol() and returns: str, str, str, str, str, str, str, str