'Return parser dictionary keyed for each columnar type
(as defined in datatypes).
.. note:: primitives only by default (str, int, float, boolean, None).
Other (more complex) types are retrieved as strings.
:returns: a dictionary of the form:
`{ <parser type name> : <function used to parse type> }`'

def get_default_parsers(self):

    return {'int': int, 'float': float, 'bool': bool}
