def contains(self, key):
try:<EOL><INDENT>self.get_loc(key)<EOL>return True<EOL><DEDENT>except KeyError:<EOL><INDENT>return False<EOL><DEDENT>
Return a boolean indicating if the key is IN the index

We accept / allow keys to be not *just* actual
objects.

Parameters
----------
key : int, float, Interval

Returns
-------
boolean