Refactoring parse_time through single dispatch.

parse_time.py

from functools import singledispatch

@singledispatch
def convert_time(time_string, **kwargs):
    # default case when no type matches
    return Time(time_string, **kwargs)

@convert_time.register(pandas.Series)
def convert_time_pandasSeries(time_string, **kwargs):
    return np.array([Time(val, **kwargs) for val in time_string])

@convert_time.register(np.datetime64)
def convert_time_npdatetime64(time_string, **kwargs):
    return Time(_parse_dt64(time_string), **kwargs)

@convert_time.register(np.ndarray)
def convert_time_npndarray(time_string, **kwargs):
    return np.array([Time(_parse_dt64(val), **kwargs) for val in time_string])

@convert_time.register(str)
def convert_time_str(time_string, **kwargs):
    # only include those string patterns which can't be handled by 
    # astropy.time.Time
    ...
    # when no format matches, call default function that is,
    # give it to astropy.time.Time to handle
    convert_time.dispatch(object)(time_string, **kwargs)

def parse_time(time_string, **kwargs):
    if time_string is 'now':
        return Time.now()
    else:
        return convert_time(time_string, **kwargs)