def __contains__(self, key):
if not isinstance(key, Interval):<EOL><INDENT>return False<EOL><DEDENT>try:<EOL><INDENT>self.get_loc(key)<EOL>return True<EOL><DEDENT>except KeyError:<EOL><INDENT>return False<EOL><DEDENT>
return a boolean if this key is IN the index
We *only* accept an Interval

Parameters
----------
key : Interval

Returns
-------
boolean