Returns the length of an input string or binary value. For strings,
the length is the number of characters, and UTF-8 characters are counted as a
single character. For binary, the length is the number of bytes.
Example:
>>> df=session.create_dataframe(["the sky is blue","WE CAN HANDLE THIS","ÄäÖößÜü",None],schema=["a"])>>> df.select(length(df["a"]).alias("length")).collect()[Row(LENGTH=15), Row(LENGTH=18), Row(LENGTH=7), Row(LENGTH=None)]