def generate_header_file(variant, Variant_df):
	"""Generates a txt file that contains sequence headers that will be used to filter sequences."""
	variant_headers = variant + ".txt"
	with open(variant_headers, "w", newline='\n') as file:
		Variant_df.taxon.to_csv(file, index=False, header=False, line_terminator='\n')
	# In GISAID, Northern_Ireland is missing its underscore so we have to adjust our file to reflect this.
	with open(variant_headers, "r") as file:
		filedata = file.read()
		filedata = filedata.replace('Northern_Ireland', 'Northern Ireland')
	with open(variant_headers, 'w', newline='\n') as file:
		file.write(filedata)
	return variant_headers