code: def col_value_type(self):
      return self.col_type._drop_fields(set(self.col_key))
  
imports: import pprint
  from hail.typecheck import typecheck_method, sequenceof
  from hail.utils.java import escape_parsable
  from hail.expr.types import dtype, tstruct
  from hail.utils.java import jiterable_to_list
label_desc: Use image node_id 13 for calling the tmatrix obj's underlying member method code with example usage: obj.col_value_type() and returns: self