class_docstr: A generic container for immutable data that can be accessed either by
  numeric index or by key. This is similar to an
  :class:`collections.OrderedDict` except that the keys are optional and
  iteration over it returns the values instead of keys.
  
  This is the base class for both :class:`.Column` and :class:`.Row`.
  
  :param values:
      A sequence of values.
  :param keys:
      A sequence of keys.
docstr: Print a unicode sample of the contents of this sequence.
docstr_tok: ["Print","a","unicode","sample","of","the","contents","of","this","sequence","."]
code: def __unicode__(self):
      """
      Print a unicode sample of the contents of this sequence.
      """
      sample = ", ".join(repr(d) for d in self.values()[:5])
  
      if len(self) > 5:
          sample = "%s, ..." % sample
  
      return f"<agate.{type(self).__name__}: ({sample})>"
  
imports: from collections import OrderedDict
  from collections.abc import Sequence
  from agate.utils import memoize
label_desc: Use image node_id 4 for calling the MappedSequence obj's underlying member method code with example usage: obj.__unicode__() and returns: str, type, str, sample, str