Human: Write me a Python function to check if a line in file exists. Assistant: 
Here is a Python function to code to check if a line in file exists

import os

def _line_in_file(file_obj, line):
    """
    >>> file_obj = open("file.txt", "r")
    >>> _line_in_file(file_obj, "This is a line")
    True
    >>> _line_in_file(file_obj, "This is not a line")
    False
    """
    return line in file_obj.read()

# Enter the file name
file_name ="yellow submarine"

# Open the file
file_obj = open(file_name, "r")

# Calling the function
line_in_file = _line_in_file(file_obj, "This is a line")

# Print the line in file

#Remember to inspect code for bugs.