<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _calc_input_estimates(keyvals, get_retriever):
 """Calculate estimations of input file sizes for disk usage approximation. These are current dominated by fastq/BAM sizes, so estimate based on that. """

    out = {}
    for key, val in keyvals.items():
        size = _calc_file_size(val, 0, get_retriever)
        if size:
            out[key] = size
    return out