def _set_item(self, key, value):
self._ensure_valid_index(value)<EOL>value = self._sanitize_column(key, value)<EOL>NDFrame._set_item(self, key, value)<EOL>if len(self):<EOL><INDENT>self._check_setitem_copy()<EOL><DEDENT>
Add series to DataFrame in specified column.

If series is a numpy-array (not a Series/TimeSeries), it must be the
same length as the DataFrames index or an error will be thrown.

Series/TimeSeries will be conformed to the DataFrames index to
ensure homogeneity.