Function duckdb_prepared_statement_column_name 

pub unsafe extern "C" fn duckdb_prepared_statement_column_name(
    prepared_statement: duckdb_prepared_statement,
    col_idx: idx_t,
) -> *const c_char

Returns the name of the specified column of the result of the prepared_statement. The returned string should be freed using duckdb_free.

Returns nullptr if the column is out of range.

@param prepared_statement The prepared statement. @param col_idx The column index. @return The column name of the specified column.