def read_methylation_file(sample_name, meth_type, head, path, chromosome):
    """
    Read file from which you want to extract the methylation level and
    (assuming it is like the Ecker/Methylpy format) extract the number of
    methylated read and the total number of read for the cytosines covered and
    in the right genomic context (CG or CH)
    Parameters
    ----------
    sample_name:
        name of the file to read to extract key information.
    meth_type:
        CG, CH or not specified
    head: if there is header that you don't want to read. An annotation in the
        file you are reading. The default value is the Methylpy/Ecker header
    path: path of the to access the file of the sample you want to read. 
    chromosome: chromosomes if the species you are considering. default value
        is the human genome (including mitochondrial and sexual chromosomes)
    """
    # open the sample file
    with open(path+sample_name) as sample:
        
        # initialize the variables
        reduced_cyt = {} # to store cyt for each chrom (intermed output)
        for c in chromosome:
            reduced_cyt[c] = []

        # specify the cytosine context you want to consider:
        if meth_type == 'CG':
            extract_CG(sample, reduced_cyt, head)
        elif meth_type == 'CH':
            extract_CH(sample, reduced_cyt, head)
        elif meth_type == '':
            for line in sample:
                line = line.split("\t")
                if line != head:
                    reduced_cyt[line[0]].append([int(line[1]),int(line[-3]), int(line[-2])])
        else:
            print ("error in the choice of methylation context")
            return()
    return(reduced_cyt)
