code: def build_expression_values(dynamizer, expr_values, kwargs):
      
      if expr_values:
          values = expr_values
          return dynamizer.encode_keys(values)
      elif kwargs:
          values = dict(((':' + k, v) for k, v in six.iteritems(kwargs)))
          return dynamizer.encode_keys(values)
docs: Build ExpresionAttributeValues from a value or kwargs