A couple of questions about counts/value_counts and pandas?

[Puxk]

why does this work

df[df['TotalPayBenefits']== df['TotalPayBenefits'].max()]

but this gives an error

df[df['TotalPayBenefits'].max()]

Error:
---------------------------------------------------------------------------
During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
<ipython-input-24-d77051c168c8> in <module>
----> 1 df[df['TotalPayBenefits'].max()]

KeyError: 567595.43

while Key Error is kind of my answer but it doesnt give me the name it corresponds with the value

now for count and value counts

df[df['AM or PM']=='AM'].value_counts()

why does this give off an error

Error:
AttributeError: 'DataFrame' object has no attribute 'value_counts'

while value_counts is definitely an attribute

and

df['AM or PM'].value_counts()

value counts work just fine here