text: from collections import Counter
  from itertools import product
  from Bio import Entrez
  def kmers_from_file(file):
      b = True
      while b:
          try:
              with open(file) as f:
                  f.readline()
                  ly = []
                  for i in f.readlines():
                      ly.append(i)
              b = False
          except:
              print('Enter the correct filename: ')
      fasta_string = ''.join([i.strip() for i in ly])
      k = int(input('Enter the value of k: '))
      counts = Counter(fasta_string[i:i+k] for i in range(0,len(fasta_string)) if len(fasta_string[i:i+k])==k)
      for k_mer in (''.join(t) for t in product('ACGT', repeat=k)):
          print(f"count of {k_mer} is {counts[k_mer]}")
  
  def kmers_from_ncbi(email):
      Entrez.email = email
      file = input('Enter the ncbi accession number: ')
      k = int(input('Enter the value of k: '))
      handle = Entrez.efetch(db = 'nucleotide', id = file,rettype="fasta", retmode="text")
      record = handle.read()
      fasta_string = ''.join(record.split('\n')[1:])
      counts = Counter(''.join(t) for t in zip(*[iter(fasta_string)]*k))
      for k_mer in (''.join(t) for t in product('ACGT', repeat=k)):
          print(f"count of {k_mer} is {counts[k_mer]}")
  