def hgnc_id(self, hgnc_symbol, build='<STR_LIT>'):
<EOL>query = {'<STR_LIT>':hgnc_symbol, '<STR_LIT>':build}<EOL>projection = {'<STR_LIT>':<NUM_LIT:1>, '<STR_LIT>':<NUM_LIT:0>}<EOL>res = self.hgnc_collection.find(query, projection)<EOL>if res.count() > <NUM_LIT:0>:<EOL><INDENT>return res[<NUM_LIT:0>]['<STR_LIT>']<EOL><DEDENT>else:<EOL><INDENT>return None<EOL><DEDENT>
Query the genes with a hgnc symbol and return the hgnc id

        Args:
            hgnc_symbol(str)
            build(str)

        Returns:
            hgnc_id(int)