I have a DataFrame in which the columns are MultiIndex and the index is a list of names, ie `index=['Andrew', 'Bob', 'Calvin',...]`.

I would like to create a function to return all rows of the dataframe that use the name 'Bob' or perhaps start with the letter 'A' or start with lowercase. How can this be done?

I looked into the `df.filter()` with the regex argument, but it fails and I get:

```
df.filter(regex='a')
TypeError: expected string or buffer

```

or:

```
df.filter(regex=('a',1)
TypeError: first argument must be string or compiled pattern

```

I've tried other things such as passing `re.compile('a')` to no avail.