def _validate_key(self, key, axis):
raise AbstractMethodError()<EOL>
Ensure that key is valid for current indexer.

Parameters
----------
key : scalar, slice or list-like
    The key requested

axis : int
    Dimension on which the indexing is being made

Raises
------
TypeError
    If the key (or some element of it) has wrong type

IndexError
    If the key (or some element of it) is out of bounds

KeyError
    If the key was not found