add conditions in the function of perpendicular_momentum

[Jiemin-Li]

Add some conditions at the beginning of the perpendicular_momentum such that (1) the input arguments must have same lengths; (2) or there is only one input argument whose length is larger than 1. @awalter-bnl Please have a look.

[awalter-bnl]

Perhaps this could be written a little more succinctly written as below. I think this will run faster than the multiple if statements that you are suggesting. But I let you decide, I have made a few other comments if you decide not to use what is below.

check_data = [len(value)
      if (isinstance(value,(np.ndarray)) and len(value.shape)==1)
      else False
      for value in [inner_value for inner_value in 
                    [parallel_momentum, photon_energy, 
                     binding_energy]
                    if not isinstance(inner_value, (float, int))]]

if not np.all(check_data_len):
    raise ValueError (f'Some string about not being an int, float or 1D numpy array')
elif check_data_len[:-1] != check_data_len[1:]:
    raise ValueError (f'Some string about all numpy arrays not being the same length')

[awalter-bnl]

This elif is not required, as inputting these as lists will not work. The reason for this is the code below uses numpy arithmetic functions which are only guaranteed to work for numpy arrays, floats or ints. If you would like lists to work add some code before this that checks for lists in these inputs and convert them to numpy arrays.

[Jiemin-Li]

Replace these lines with the new codes.

[awalter-bnl]

Looks good @Jiemin-Li , thanks for the PR