How remove column name from null value record

Hi

I am working on ruby coding in watson appbuilder tool.

I want to remove if the column name is null then remove that from column
list so it won’t show empty spaces.

for example:

custid :123
custname : john T
phone number :765-456-0987
birthdate : 12/3/1989
address : asdfgjhkk

suppose phone number field is null

then it is showing

custid :123
custname : john T
phone number :
birthdate : 12/3/1989
address : asdfgjhkk

I want following …please let me know what will be the code for
following:

custid :123
custname : john T
birthdate : 12/3/1989
address : asdfgjhkk