<human>:  replace substring in a string with another substring.
<bot>: Here is a Python function to replace a substring in a string with another substring

import re

def replace_substring(string, old_substring, new_substring):
  """
  Replaces substring in a string with another substring.

  :param string: input string
  :type string : str
  :param old_substring: old substring
  :type old_substring : str
  :param new_substring: new substring
  :type new_substring : str
  :return: string
  """
  return string.replace(old_substring, new_substring)

# Enter the string
string = "Hello World"

# Enter the old substring
old_substring = "Hello"

# Enter the new substring
new_substring = "Goodbye"

# Calling the function
print((replace_substring(string, old_substring, new_substring)))

#Example Output
# Goodbye World

#Remember to inspect code for bugs.