<human>:  What is a good Python program for caching if the string is custom date.
<bot>: Here is a Python program for checking if the string is a custom date

import datetime

def is_custom_date(string):
  """Check if string is custom date."""
  if string.startswith('2019-'):
    return True
  return False

# Enter the string
string = '2019-01-01'

# Calling the function
print((is_custom_date(string)))

#Example Output
# True

#Remember to inspect code for bugs.